First, find the price of cherries and strawberries per pound.

2 lbs of cherries = $3.50 = 350 cents

1 lb of cherry = cents =$1.75

3 lbs of strawberries = $4.71 = 471 cents

1 lb of strawberries = cents = $1.57

So, she buys 3 lbs of cherries and 4 lbs of strawberries to pay:

Add a 2% tax to this amount:

Note: 2% tax on $11.53 = . This is the tax that she pays(23 cents)

Rounding off to the nearest cents gives you: $11.76

So she gives a $20 bill means she gets back, $20.00 - $11.76 = $8.24