Try this explanation/solution:
a) the system which describes this situation is:

b) the solution of the system made up:

Answer:
3/4 pizza is left. If you want an explanation, ask me ;>
Answer:
C. 5
Step-by-step explanation:
first expression 5 × (9-3) = 30
second one 45 - 3x
to make it 30 = 30
x should be = 5
Answer:
here is the correct answer