He simultaneous equations5x + y = 21x - 3y = 9 with working out

see explanation

Step-by-step explanation:

Given the 2 equations

5x + y = 21 → (1)

x - 3y = 9 → (2)

Multiply (1) by 3 and add the result to (2) to eliminate y term

15x + 3y = 63 → (3)

Add (2) and (3) term by term

(x + 15x) + )- 3y + 3y) = (9 + 63)

16x = 72 ( divide both sides by 16 )

x = 4.5

Substitute x = 4.5 into (1) for corresponding value of y

22.5 + y = 21 ( subtract 22.5 from both sides )

y = - 1.5

Solution is (4.5, - 1.5 )

x=4

step-by-step explanation: