A Trapezoid Has One Base Of 10cm, Height Of 7cm And Area Of 56 Sq Cm. What Is The Length Of The Second Base (in Cm)?

The formula of the area of a trapezoid is:
Area=a[(b1+b2)/2]
Where:
b1= first base
b2= second base
a=height
In the question we are given that:
b1=10
a=7
Area=56
Plugging in these values in the formula to obtain b2:
Area=a[(b1+b2)/2]
56=7[(10+b2)/2]
Expanding:
56=[70+7b2]/2
shifting 2 to the other side:
56*2=70+7b2
112=70+7b2
112-70=7b2
Subtracting:
42=7b2
dividing:
b2=42/7
So:
b2=6
So the length of the second base is 6 cm