Question

X + y = 7 x = 4y – 8

Answer 1

X = 4 ; Y = 3

Explanation:

x = 8 − 4y

X= 4

Y= 7-x

Y=7-4

Y= 3

4 + 3 = 7 4 = (4x3) – 8

The systems of equations can be solved by several methods: substitution, opposite coefficients, graphs, determinants, etc. All methods lead to the same solution, and which of them will depend on the task setting (you should choose the method that seems to be the most suitable for the task).

We used here Substitution method

Procedure: choose one of the two given equations and express one from the unknown over the other unknown and then replace the unknown in the other equation with the obtained expression. In this way one equation with one unknown is obtained.

Tip: When selecting the unknown one should choose one that has a coefficient (number) in front of it that facilitates the account.

Answer 2

x = 4, y = 3

Explanation:

x + y = 7 (1)

x = 4y – 8

Rearrange

x — 4y = —8. (2)

Solving by elimination method:

Subtract equation 2 from equation 1

x + y = 7

— ( x — 4y = —8)

5y = 15

Divide both side by the coefficient of y i.e 5

y = 15/5

y = 3

Substitute the value of y into equation 1,we have:

x + y = 7

x + 3 = 7

Collect like terms

x = 7 — 3

x = 4

x = 2, y = 3