Aa pencil and a ruler cost a dollar fifty together the ruler cost a dollar more than the pencil how much does a pencil cost

Use the following variables:
P = pencil
R = ruler

P + R = 1.50

R = P + 1.00

Plug in the Equations:

P + (P + 1.00) = 1.50

2P + 1.00 = 1.50

2P = 0.50

P = 0.25

R = 1.50 - 0.25

So the pencil costs $0.25 and the ruler costs $1.25