According to Mark and Luke, there was only one demoniac who approached Jesus. There was a legion of demons speaking through him (Mk 5:12; Lk 8:31). From Matthews account, one can infer that the legion of demons spoke to Jesus all at once (Mt 8:29, 31). Again, we see that the accounts come quite close to each other.
Could it be that Mark and Luke mentioned only one demoniac because only one approached Jesus, or maybe because he was more ferocious than the other one or had more demons? Possibly. But it doesnt seem to be the main reason. The clue seems to appear at the end of Mark and Lukes accounts where only one of the healed returned to thank Jesus and asked if he could follow him. When Jesus said no, he went off and started talking about what had happened (Mk 5:1820; Lk 8:3839).
From this perspective, the differences in the accounts of the evangelists seem negligible.
The withered fig tree
On Monday of Holy Week, Jesus was hungry and, coming up to a fig tree and finding no fruit, cursed it (Mt 21:1822; Mk 11:1214, 11:2026; UG 143, 145). According to Matthew, the fig tree withered immediately (Mt 21:19). Then he says, «And when the disciples saw it, they marvelled, saying, How soon is the fig tree withered away!» (Mt 21:20). In Mark, the apostles found the fig tree withered only on the following morning (Mk 11:20). Is there an irreconcilable contradiction here?
Since Mark specifies the moment of discovering the withered fig tree precisely (Mk 11:20) and Matthew is vague (Mt 21:20), it would make sense to give preference to Marks version here. As to the actual time the fig tree withered, Matthew seems more accurate (Mt 21:19) while Mark only mentions that the disciples heard the curse (Mk 11:14).
We might speculate that the fig tree withered soon after Jesus had cursed it, but the disciples only saw it the next day. In this case, the apparent contradiction is removed.
Generally, the two evangelists present their narratives differently. Mark relates the story in chronological order, capturing Peters memories in exact detail. Matthew tells the fig tree story in the form of a parable, alluding to Lukes parable of the barren fig tree (Lk 13:69; UG 113). That is why Matthew presents the episode as a whole, while Mark divides it up into two parts with the story of the temple cleansing stuck in between (Mk 11:1519; compare Mt 21:1217; Lk 19:4546; UG 144). Matthew places the fig tree account after the account of driving out the merchants because the ending of the fig tree story happened after it. This may give the impression that Jesus first drove out the merchants and then cursed the fig tree, but in Mark, the cursing of the fig tree preceded the cleansing of the temple. This «inconsistency» can be explained by Matthews desire to present the story in the form of a parable.