Question

Use the linear equations below to answer questions 51 & 52. (HINT: Solve by the

Substitution method - you must first solve for x !!!).
x + 3y = 7
4x-y = 15
a) What is the value of x?
b) What is the value of y?

Answer 1

x = 4

y = 1

Explanation:

x + 3y = 7 --> Eq1

4x - y = 15 --> Eq2

Find x in term of y using Eq1

x = 7 - 3y

Substitute x in Eq2

4(7-3y) -y = 15

28 - 12y - y = 15

-12y-y = 15 - 28

-13y = -13

y = -13/-13

y = 1

Find x

x = 7-3(1) = 4

If you have to solve for x first

Find y in term of x using Eq 2

y = 4x - 15

Substitute y in Eq 1

x + 3(4x -15) = 7

x + 12x - 45 = 7

x + 12x = 7 + 45

13x = 52

x = 52/13

x = 4

Find y

y = 4(4) -15 = 16 - 15 = 1