Stanley bought a ruler and a yardstick for $1.25. If the yardstick cost 45 cents more than the ruler

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Stanley bought a ruler and a yardstick for $1.25. If the yardstick cost 45 cents more than the ruler, what was the cost of the yardstick?

Let r be the cost of the ruler
Let y be the cost of the yardstick

We're given 2 equations:

1. r + y = 1.25
2. y = r + 0.45

Substitute equation (2) into equation (1) for y
r + r + 0.45 = 1.25

Solve for r in the equation r + r + 0.45 = 1.25

Step 1: Group the r terms on the left hand side:
(1 + 1)r = 2r

Step 2: Form modified equation
2r + 0.45 = + 1.25

Step 3: Group constants:
We need to group our constants 0.45 and 1.25. To do that, we subtract 0.45 from both sides
2r + 0.45 - 0.45 = 1.25 - 0.45

Step 4: Cancel 0.45 on the left side:
2r = 0.8

Step 5: Divide each side of the equation by 2
2r/2 = 0.8/2

r = 0.4

Substitute r = 0.4 into equation (2) above:
y = r + 0.45
y = 0.4 + 0.45
r = 0.85

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