Arithmetic sequence with d = 18
26 + 44 + 62 + 80 + 98 + 116 + 134 = ad 'em up to see what you get !
Or use SUM = n ( a1+a7)/2 = 7 (26+134)/2 = ??
4.) d = 5 so 5n is good..... first one starts with 54 ...no good second choice only has 13 terms...no good
third choice starts with 49 and has 5n and has 14 terms.....goood! Fourth choice has 44 terms....no good
5.
n =1 = 5
2 =6
3 7
4 8 Add 5 6 7 8 and you get ?