The canvases cost $40.00 and she spent half that amount on paint so she spent 40/2 = $<<40/2=20.00>>20.00 on paint

She spent $40.00 on canvases, $20.00 on paint and $15.00 on an easel so she spent 40+20+15 = $<<40+20+15=75.00>>75.00

She spent $90.00 total and her other purchases totaled $75.00 so she spent 90-75 = $<<90-75=15.00>>15.00 on paint brushes

# Answer

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<|im_start|>system
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<|im_start|>user
Tonya spent $90.00 on art supplies.  4 canvases cost $40.00 and a mixed set of paints cost 1/2 that much. She also spent $15.00 on an easel, and the rest of the money on paintbrushes. How much money did she spend on paintbrushes?
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<|im_start|>assistant

user
15
Tonya spent $90.00 on art supplies.  4 canvases cost $40.00 and a mixed set of paints cost 1/2 that much. She also spent $15.00 on an easel, and the rest of the money on paintbrushes. How much money did she spend on paintbrushes?
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