What is the answer to this problem evaluate the expression 7.5-3.2+4^3÷2

Step 1 solve 4^3 which is 64 so you then have 7.5-3.2+64/2
step 2 you divide 64/2= 32 so you then have   7.5-3.2+32  
step 3 subtract 7.5-3.2= 4.3 so you then have    4.3+32  
step 4 add 4.3+32= 36.3  so the final ANSWER is 36.3

No solution : there is no number of boxes that she bought