To subtract 7/10 by 1/2, you need to find the common denominator. In this case, the common denominator would be 10. Multiply 1/2 by 5/5, which gives you 5/10. Now you can subtract 7/10 and 5/10.
Once you finish subtracting, you should get 2/10. This answer can be simplified to 1/5.
