Answer:
Sam's student council spent $39 on backpacks + paper and pens.
Explanation:
They bought 3 backpacks for $7 each. 3 x 7 = $21.
They also filled those backpacks with paper and pens costing $6 each. 3 backpacks x $6 = $18.
Now, add the two prices.
18 + 21 = 39
hope this helps :)