Question

Below, explain why we are allowed the"substitute in" x - 3 for y in the top equation.Why is this useful for finding our first solution?x + x = 11y = 1x - 3

Answer 1

You have the following system of equations:

x + y = 11

y = x - 3

it is usefull to replace the expression y = x - 3 into the first equation, because in this way you can solve for x, just as follow:

x + x - 3 = 11 here you replaced y = x - 3. Simplify like terms:

2x - 3 = 11

2x = 11 + 3

2x = 14

x = 14/2

x = 7