H=Hours he an skate; T=total cost
T=$7.00+($1.50/hr)H
T-$7.00=($1.50/hr)H
(T-$7.00)/($1.50/hr)=H
For T=$19:
($19.00-$7.00)/($1.50/hr)=H
$12.00/($1.50/hr)=H
8hrs=H
ANSWER: Jon can skate 8 hours for $19.00.
Hope this helps!
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