Question

4x+3y=20 2x+y=7 How do I solve this? I forgot how to do it :/ also no answer choice

Answer 1

So for this, I will be using the substitution method. Firstly, subtract both sides in the second equation by 2x: $4x+3y=20\\ y=7-2x$

Next, substitute y in the first equation with 7-2x, then solve for x from there:

$4x+3(7-2x)=20\\ 4x+21-6x=20\\ -2x+21=20\\ -2x=-1\\ x=\frac{1}{2}$

Now that we got x, substitute it into either equation to solve for y:

$4*\frac{1}{2}+3y=20\\ 2+3y=20\\ 3y=18\\ y=6\\ \\ 2*\frac{1}{2}+y=7\\ 1+y=7\\ y=6$

In short, x = 1/2 and y = 6.