Question

solve using substitution

x+y=7
5x+4y=3

Answer 1

x = 7 - y

5(7 - y) + 4y = 3
35 - 5y + 4y = 3
-y = -32
y = 32
x = 7 - y
x = -25

x = -25
y = 32

Answer 2

see there are two methods of solving these two substitutions given:
one is column method and other is that chiaroscuro did. Both of them are approx. same
x+y = 7
transposing y to RHS or subtracting both sides by y we will get
x = 7-y
now putting the value of x on the place of the second substitution:
5(7-y) + 4y = 3
35 - 5y + 4y = 3
35 - y =3
-y = 3 - 35
-y = -32
-1(y) = -32
y = -32/-1
y = 32