Question

0.3x + 0.2y = 5,
0.5x + 0.4y =11

Answer 1

Eqn 1
0.3x + 0.2y = 5
0.2y = 5 - 0.3x
0.4y = 10 - 0.6x

Eqn 2
0.5x + 0.4y = 11
0.4y = 11 - 0.5x

10 - 0.6x = 11 - 0.5x Substitute Eqn in to eqn 2
10 - 11 = -0.5x + 0.6x rearrange
-1 = 0.1x
-10 = x x = -10

0.4y = 11 - 0.5(-10) = 11 + 5 = 16
0.4y = 16
(10/4)(4/10)y = y = (10/4)(16) = 40

checking:
x = -10, y = 40

0.5(-10) + 0.4(40) = -5 + 16 = 11 Correct!