#### Answer

a. $R=7.50(x)+250$
b. 1000 dollars
c. $P=2.21x-150$
d. 71 dollars
e. 68 photos

#### Work Step by Step

a. R=revenue, x=number of proofs
$R=7.50(x)+250$
b. x=100
$R=7.50(100)+250$
$R=750+250$
$R=1000$
c. P=profit, C=cost (C=5.29(x)+400)
$P=R-C$
$P=(7.50x+250)-(5.29x+400)$
$P=7.50x+250-5.29x-400$
$P=2.21x-150$
d. x=100
$P=2.21(100)-150$
$P=221-150$
$P=71$
e. P=0
$0=2.21(x)-150$
$0+150=2.21(x)$
$150=2.21(x)$
$150\div2.21=x$
$x=67.87$ so x=68