Selma spent 7/10 of her allowance on a new backpack. what percent of her allowance did she spend?

70%
Explanation below:

To find the percent, you have to divide the fraction to get the decimal, so that the decimal can be turned to a percent.

7/10 is .70
To get the percent, you have to move the decimal 2 spaces to the right.
.70 is 70%

(7/10) allowance
* 100% = 70%
   1 allowance