Solve by subtitude 5a +2b = 20

Question

2a + b = 11

Answer 1

In second equation subtract 2 a to both sides.

b = 11 - 2 a

Put this in first equation.

5 a + 2 b = 20

5 a + 2 ( 11 - 2 a ) = 20

5 a + 22 - 4 a = 20

a + 22 = 20

Subtract 22 to both sides

a = - 2

You still knov:

b = 11 - 2 a

so

b = 11 - 2 • ( - 2 )

b = 11 + 4

b = 15

The solution is:

a = - 2 , b = 15