Question

Solve 12x+4y= 20 for A. y=-3x + 5 B. y= 12x + 5 C. y=-3x+ 20 D. 12:20

Answer 1

The question gives us an expression:

`12x+4y=20`

We are told to solve for y. This means making y the subject of the formula.

Let us perform these operations below:

`\begin{gathered} 12x+4y=20 \\ 4\text{ is common in the whole expression} \\ 4(3x)+4(y)=4(5) \\ \text{This means we can divide both sides by 4} \\ (1)/(4)\mleft(4(3x)+4(y)\mright)=(1)/(4)(4(5)) \\ \\ (4(3x))/(4)+(4y)/(4)=(4\mleft(5\mright))/(4)\text{ (4 crosses out)} \\ \\ 3x+y=5 \\ \text{Subtract 3x from both sides} \\ 3x+y-3x=5-3x \\ 3x-3x+y=5-3x \\ y=-3x+5\text{ (Option A)} \end{gathered}`

Therefore the final answer is:

y = - 3x + 5