Answer :
30 hours($7.75) + $12.50x = $400
$232.50 + $12.50x = $400
$12.50x = $400 - $232.50
$12.50x = $167.50
Divide both sides by $12.50
x = $13.4 hours
$232.50 + $12.50x = $400
$12.50x = $400 - $232.50
$12.50x = $167.50
Divide both sides by $12.50
x = $13.4 hours