Question

Solve the system using substitution.

6+8y=30
y=12x

A. 6, −3/4
B. 3, 3/2
C. (1, 3)
D. (6, 3)

Answer 1

B

Explanation:

6x + 8y = 30

y = ½x

6x + 8(½x) = 30

6x + 4x = 30

10x = 30

x = 3

y = 3/2

Answer 2

(1/4, 3)

Explanation:

Substitution is essentially where we write one variable in terms of another, substitute that into the other equation so that we are left with 1 variable, and then solve for that variable.

Here, the second equation already shows y written in terms of x: y = 12x. Substitute this into the first equation:

6 + 8y = 30

6 + 8 * (12x) = 30

6 + 96x = 30

96x = 24

x = 24/96 = 1/4

Plug this into any of the equations to solve for y:

y = 12x

y = 12 * (1/4) = 3

The answer is (1/4, 3). *Note that none of the answer choices matches this, which means that you may have copied the answer incorrectly.*