Shapes of Algebra ace help inv 4

soa inv 4 prob 51-55
soa inv 4 prob 59
soa inv 4 65 and 66

For # 20, all you do is to substitude y in for x so you get
7y - 2y = 5
5y = 5
y = 1
Since x = y, then x also = 1
the lines cross at (1,1)