Question 994233
.
x=total minutes of use
.
When x>900:
Bill=$80+$0.40(x-900)
Bill=$80+$0.40x-$360
Bill=$0.40x-$280
.
$110.40=$0.40x-$280
$390.40=$0.40x
976=x
ANSWER: He used the phone 976 minutes.