Question

A system of equations is given below:

y = 4x − 3
2x + 7y = 41

Which of the following steps could be used to solve by substitution?

2(y = 4x − 3) + 7y = 41
4x − 3 = 2x + 7y
2x + 7(4x − 3) = 41
2(y = 4x − 3)

Answer 1

C.

Explanation:

Answer 2

The given system of equations is:

y = 4x − 3 ...(1)

2x + 7y = 41 ...(2)

Notice that the first equation is a solved equation for y. So, we can simply substitute 4x-3 for y in equation (2) to solve. This method is also knwon as substitution method by which we can plug in one equation into other equation.

So, if we will substitute y=4x-3 in equation (2) then we will get,

2x+7(4x-3)=41

Hence, third choice 2x + 7(4x − 3) = 41 is the correct answer.