Answer:
A pack of pencil' price=$8
Price went up=$12
increasing percentage = change/original x100
= (12 -8)/8 x100
=4/8 x100
=50%
Answer:

Step-by-step explanation:
Here first open the inner parentheses and use the distributive property,

Answer:
Our two numbers are 50 and 20
Step-by-step explanation:
Sum means add together
Difference means subtract each other
x + y = 70
x - y = 30
subtract from each other
2x = 100
divide both sides by 2
x = 50
our first number is 50
50 + y = 70
subtract both sides by 50
y = 20
Our two numbers are 50 and 20