Question

How do I use substitution to solve the system? Please help Addition and equal key is not working . It's asking for x equals and y equals.


-5x plus 2y equal 16
y equal 2x plus 7

Answer 1

-5x +2y = 16 eq'n 1
y = 2x + 7 eq'n 2

sol'n

sub eq'n2 to eq'n 1

-5x + 2(2x +7) = 16
-5x + 4y +14 = 16
-x = -14+16
x = -2 ---> sun to eq'n 2

y = 2(-2)+7
y = 3

Answer 2

-5x + 2y = 16
y = 2x + 7

To do substitution, choose an equation and from that equation, choose a variable and express it in terms of the other. Then substitute that expression to the other equation.

Here, let's choose the second equation.
y = 2x + 7

Then let's choose the variable, y. It's already expressed in terms of the other variable, x.
y = 2x + 7

Then substitute it to the other equation:
-5x + 2y = 16
-5x + 2(2x + 7) = 16
-5x + 4x + 14 = 16
-x + 14 = 16
-x = 16 - 14
x = -2

Now that you have a value for x, substitute it to either equation and solve for y.