Question

We have two equations
$3x–4y=1$ ---------- (1)
$5x–6y=7$ ---------- (2)
In the above equations, to eliminate the coefficients of x, what has to be done?

• A. Multiply equation (1) by 6 and equation (2) by 4
• B. Multiply equation (1) by 3 and equation (2) by 5
• C. Multiply equation (1) by 5 and equation (2) by 3
• D. None

Answer 1

The correct option is C

Multiply equation (1) by 5 and equation (2) by 3

Coefficient of x in equation (1) is 3
Coefficient of x in equation (2) is 5
So, to make x coefficients equal, multiply equation (1) by 5 and equation (2) by 3.
$Equation\left(1\right)\times 5\Rightarrow 15x–20y=5$
$Equation\left(2\right)\times 3\Rightarrow 15x–18y=21$