Answer:
[tex]\large\boxed{h=\dfrac{2A}{b_1+b_2}}[/tex]
Step-by-step explanation:
[tex]A=\dfrac{1}{2}h(b_1+b_2)\qquad\text{multiply both sides by 2}\\\\2A=2\!\!\!\!\diagup\cdot\dfrac{1}{2\!\!\!\!\diagup}h(b_1+b_2)\\\\2A=h(b_1+b_2)\qquad\text{divide both sides by}\ (b_1+b_2)\\\\\dfrac{2A}{(b_1+b_2)}=\dfrac{h(b_1+b_2)}{(b_1+b_2)}\qquad\text{cancel}\ (b_1+b_2)\\\\\dfrac{2A}{b_1+b_2}=h\to h=\dfrac{2A}{b_1+b_2}[/tex]
