Question

ABCD is a parallelogram. If AB = 3x and CD = x+10, find AB

Answer 1

A parallelogram by definition is a four-sided figure with opposite sides that are parallel.

If that's the case, the length of opposite sides should be the same as well, meaning that:

$AB=CD$

then,

$\begin{gathered} 3x=x+10 \\ \text{solve for x} \\ 3x-x=10 \\ 2x=10 \\ x=\frac{10}{2} \\ x=5 \end{gathered}$

find AB

$\begin{gathered} AB=3x \\ AB=3\cdot5 \\ AB=15 \end{gathered}$

A