Answer: Tom will pay $20.01 lesser than the original price.
Explanation:
The original price of the phone is $137.99. It is now on sale for 1/10 off the original price. This means that the discount on the original price is 1/10 × 137.99 = 13.799. The new price will be the original price - the discount.
The new price is 137.99 - 13.799 = $124.191
Tom has a coupon for an extra 5% off the sale price. It means that Tom would pay 5% off $124.191. The amount that Tom would pay will be
124.191 - (5/100 × 124.191) = 124.191 - 6.20955 = $117.98
The difference between the original price and the price that Tom will pay is
137.99 - 117.98 = $20.01