Let r be the cost of the ruler

Let y be the cost of the yardstick

We're given 2 equations:

- r + y = 1.25
- y = r + 0.45

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**

Source

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