To solve that question you need to figure out how much 1 and 1/2 pounds is compared to 3 and 3/4 pound, and then use that ratio to get the price.
1 and 1/2 pound = 1.5 pound
3 and 3/4 pound = 3.75 pound
1.5/3.75 = 0.4
That means she needs to pay 0,4 of the price of 3 and 3/4 pound
0.4 * 6.88 = 2.75
So the answer is that she needs to pay $2.75 for 1 and 1/2 pound of spinach
