Question

If a + 3b = 13 and a + b = 5, the value of b is 1) 1 3) 4.5 2) 7 4) 4

Answer 1

To find the value of b we solve the first equation for a, then we have:

$a=13-3b$

now we plug this value into the second equation:

$\begin{gathered} (13-3b)+b=5 \\ 13-2b=5 \\ 13-5=2b \\ 2b=8 \\ b=\frac{8}{2} \\ b=4 \end{gathered}$

Therefore b=4