a) Same-side interior angles
b)

c) They are parallel by the same-side interior angles theorem.
Answer: cheese pizzas = 25 , Pepperoni pizzas = 15
Step-by-step explanation:
Let x = Number of cheese pizzas, y = Number of pepperoni pizzas.
As per given,

Multiply 7 on both sides of (i), we get

Eliminate (iii) from (ii), we get

Put value of y in (i) , 
Hence, cheese pizzas = 25 , Pepperoni pizzas = 15
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