Sue spent half of her money on a book. then she spent $1.25 on a pen. she has $3.20 left. how much did she start with?

She started with 8.90

Step-by-step explanation:

Let m = money

She spent 1/2 on a book

m - 1/2 m

This is what she has left after buying her book

Now she buys a pen at 1.25

m-1/2m - 1.25

This is how much she has left after buying the pen

The problem states that she has 3.20 left

3.20 = m-1/2m - 1.25

Combine like terms

3.20 = 1/2 m - 1.25

Add 1.25 to each side

3.2+1.25 = 1/2m -1.25 +1.25

4.45 = 1/2m

Multiply by 2

2*4.45 = 1/2m*2

8.90 = m

She started with 8.90

i hope this is what you were looking for.

see attached graph

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