$2x + 4y = 12
{ y=2
y = 2

a) 9

Step-by-step explanation:

Draw out or imagine the next set of pyramids. If P1 has 2 blocks on the bottom and P2 has 3 blocks, that means that if you follow the pattern, P4 will have 5 blocks on the bottom so just add 5 to the amount of blocks in P3. To make P5, just add 6 blocks onto the amount of blocks in P4 that you just made. Hope this helps, I am not very good at explaining. I don't know the answer to 'b' as I am struggling with it as well.