Answer:
Jess used 40 blocks in total.
Step-by-step explanation:
First stack: 8 blocks
Second stack: First stack + 4 = 8 + 4 = 12 blocks
Third stack: Second stack + 8 = 12 + 8 = 20 blocks
Total number of blocks: First stack + Second stack + Third stack = 8 + 12 + 20 = 40 blocks