66x12=792 pupils can ride on 12 buses
Answer:

Step-by-step explanation:
This situation can be represented by
y = 33x + 223
y = 32x + 239
I still like substitution, so let’s plug in 33x + 223 into the second equation
33x + 223 = 32x + 239
Move the terms into appropriate sides
33x - 32x = 239 - 223
Combine like terms
x = 16
Then plug in x for any equation
y = 32(16) + 239
y = 751
Erin will have to swim 16 laps for a total of 751 meters
I will do (a) only.
6rt - 3st + 6ru - 3su
6rt - 3st = 3t(2r - s)
6ru - 3su = 3u(2r - s)
Answer: (3t + 3u)(2r - s)
Do the rest likewise.