In order to solve the following system of equations by subtraction, which of
the following could you do before subtracting the equations so that one
variable will be eliminated when you subtract them?
4x – 2y=7
3x – 3y=15

A. Multiply the top equation by-3 and the bottom equation by 2.

B. Multiply the top equation by 1/3.
C. Multiply the top equation by 3 and the bottom equation by 4.

D. Multiply the top equation by 15 and the bottom equation by 7.

I think it's C.Multiply the top equation by 3 and the bottom equation by 4

Step-by-step explanation:

Multiplying the top equation by 3 you get:

3(4x – 2y) = 3∗7

12x - 6y = 21          (eq.1)

Multiplying the bottom equation by 4 you get:

4(3x – 3y) = 4∗15

12x - 12y = 60       (eq.2)

Now, if you subtact eq.2 from eq.1 you get:

(12x - 6y = 21 )

-

(12x - 12y = 60)

0x + [- 6y -(-12y)] = 21 - 60

Carrying out the calculation you get:

6y = -39

y = -39/6

y = -13/2

for ex: the reciprocal of 3/4 is 4/3. it is the opposite.

reciprocal definition:

a mathematical expression or function so related to another that their product is one; the quantity obtained by dividing the number one by a given quantity.