You have to make an inequality:
1.2x + 6 ≤ 20
- 6 - 6 isolate x
1.2x ≤ 14
÷1.2 ÷1.2 isolate x
x ≤ 11.666
Since you can't buy 2/3 of a pack, she can only buy 11 pieces of gum.
Hope this helps!
623. First find the volume of the rectangular prism, then find the volume of the cube. divide the volume area of the prism volume of the cube