Matthew S. answered • 02/21/20

PhD in Mathematics with extensive experience teaching Linear Algebra

Let a := # panels produced by plant A; b := # panels produced by plant B

The problem statement gives us two equations in a & b:

0.02a + 0.05b = 1300

a - b = -5000

I you multiply both sides of the first equation by 50, you get

a + 2.5b = 65000

Subtracting the second equation from this new equation, you get

3.5b = 70000

Therefore b = 20000 units.