#1
88+100+72+94=354 ---first 4 tests total
if he needs an average of 90, the total of 5 tests must = 90x5=450
450 - 354 = 96
answer: his last test he needs to make 96 in order to average 90
#3
n, n+2, n+4 are 3 consecutive even numbers
4(n+n+2) = 2(n+4)
4(2n+2)=2(n+4)
8n+8 = 2n + 8
6n = 0
n = 0
n+2=0+2=2
n+4=0+4=4
answer: 3 consecutive even numbers are 0,2,4
double check
4 times sum of first and second equals twice the third
4(n+n+2) = 2(n+4)
4(0+0+2)=2(0+4)
4(2)=2(4)
8=8
