The original price of the tent will be called "x". The store increased the value by 25%, so the new value is the original one plus 0.25 of the original one, so the new value is 1.25*x. The costummer paid the increased value less the $10 from the coupon, so we have:
paid = 1.25*x - 10
Since he paid $152.5 for the tent we can compute the original value as shown bellow: