First, find common denominators
(3/4)(4/4) = 12/16
(3/8)(2/2) = 6/16
12/16k + 6/16k = 12
Simplify. Combine like terms
18/16k = 12
Isolate the k. Multiply 16/18 to both sides
(18/16)k(16/18) = 12 (16/18)
k = 12(16/18)
Multiply 12 with 16, then divide by 18
12 x 16 = 192
192/18 = 10.67 (rounded)
10.67 = 10 67/100 is your answer
hope this helps