Answer:
[tex]38[/tex] units long
Step-by-step explanation:
The Area formula for a trapezoid is [tex]\frac{a+b}{2} h[/tex]
Where a and b are the 2 bases
We fill in what we know first
[tex]348=\frac{a+20}{2} (12)[/tex]
Divide both sides by 12
[tex]29=\frac{a+20}{2}[/tex]
Multiply both sides by 2
[tex]58=a+20[/tex]
Subtract both sides by 20
[tex]38=a[/tex]
The second base is 38 units long
I hope this helps please let me know if you have any further questions
