Question

Find the solution to the following system by substitution.

5x + y = 20
y = 5x

A. (2,10)
B. (4,0)
C. (0,20)
D. (4,20)​

Answer 1

Answer: A. (2, 10)

Explanation:

=> 5x + y = 20 (Eq. 1)
=> y = 5x (Eq. 2)

Substitute value of ‘y’ from Eq. 2 in 1 :-

5x + y = 20
5x + (5x) = 20
10x = 20
x = 20/10
=> x = 2

Therefore, x = 2

Substitute value of ‘x’ in Eq. 2 :-

y = 5x
y = 5(2)
=> y = 10

Therefore, y = 10

Hence, x = 2 and y = 10 (2, 10)

Answer 2

A. (2,10)

Explanation:

5x + y = 20

y = 5x

The second equation is already solved for y, so substitute 5x for y in the first equation to find x.

5x + 5x = 20

10x = 20

x = 2

Now substitute 2 for x in the second original equation to find y.

y = 5(2)

y = 10

Answer: (2, 10) which is A.