i got this because the first part says 13 × 3/8 so this means that the numbers 2 × 3/8 + 3/8 + 3/8 and the unknown number have to equal 13. so when u multiply 2 x 3/8 you get .75 and then you add the two other numbers and get 1.5 and then you subtract 1.5 from 13 and you get 11.5
