It’s C mate! Hope this helps! :))
The next three numbers are 48, 44, 176
1/3 x 4/4 = 4/12
4/12 + 5/12 = 9/12
12/12 - 9/12 = 3/12
3/12 = 1/4
L: 1750, M:1750-480=1270
Lisa gave some stamps to Mark so Lisa now has 1750-x and Mark has 1270+x. Mark also has 3 times as many as Lisa now: (1750-x)*3=1270+x
5250-3*x=1270+x
4*x=3980, x=3980/4, x=995
So Lisa gave 995 stamps to Mark.
At first Mark had 1270 stamps. Lisa now has 1750-995=755 stamps.
In an arithmetic sequence, the difference between consecutive terms is always the same. For example, the sequence 3, 5, 7, 9 ... is arithmetic because the difference between consecutive terms is always two.