I need help with this question

Question

Alvin and his friend are working together on a group homework assignment. Alvin has completed 1/6 of the problems and his friend has completed another 7/10 of them. Together, what fraction of the problems have they completed so far?

Answer 1

1/6 + 7/10

= 5/30 + 21/30

= 26/30

= 13/15

or in decimals

1/6 = 0.1666...

7/10 =0.7

sum =0.7 + 0.1666.... = 0.8666...

13/15 = 0.8666... = about 87%