Granny georgette and kiwi have a combined age of 77. if kiwi is 13 years less than twice granny georgette's age, how old is kiwi?

Since they decided to be extremely ridiculous and deleted my answer for "not showing enough work", here I am again:

Since it says that Kiwi is 13 less than TWICE Granny's age, I divided 77 (Granny's age) by 2, which gave me 38.5

I then subtracted 13, since it says that she is thirteen less than that number, which gave me 25.5

I had originally said "20 or 20 and a half years old" because depending on your format of testing/worksheet, you may not have the option of putting halves.