Question

How would I go about solving 12,15,18 thanks

Answer 1

for 12, you would do 90=4x+42, and 48=4x, and x=12
for 15, you would do 90=8x+66, and 24=8x, and x=3
for 18, you would do 90=3x+57, and 33=3x, and x=11