In order to find b1 from your formula stated we need to do few calculations
A=hb1+hb2, as you wee I multiply h with both bases( b1 and b2)
I will subtract hb2 from both sides
hb1=A-hb2
now I will divide my new expression by h
b1=(A-hb2)/h
7k/3 = 21
x 3 x3
7k = 63
/7 /7
k = 9
(7(9)/3 = 21 = 63/3 = 21 = 21 = 21)
Each bullet would cost 100/80 = $1.25 if 100 bullets cost $80.
I did this manually on some notepaper but my scanner is not working.
The answer is 72 cm^2