Solve each system with substitution 1 7x 4y 3 5x 25 2 8x

Solve each system with substitution

1. 7x + 4y = 3

5x = 25

2. 8x - 5y = -31

y = 3

1.
7x + 4y = 3 ....eqn 1
5x = 25
---------------------------------
5x=25 gives
x=5

put this in eqn 1
7x + 4y = 3
7*5 + 4y = 3
35 + 4y = 3
4y = -32
y = -8
Answer:
x=5 and y=- 8

2.
8x - 5y = -31 ..eqn 1
y = 3
put y=3 in eqn 1
8x - 5y = -31
8x - 5*3 = -31
8x = -16
x = -2
Answer:
x=-2
y=3