find the missing number: 12/34=?/17, 2/?+8/36?

Answer 1

For the first equation, you take half the denominator (34) to get 17. So take half the numerator (12) to get 6.

12 ... 6
--- = ---
34 .. 17

For the second equation, you multiply the numerator (2) by 4 to get 8. So the denominator should multiply by 4 to get 36. In other words, it must be 9.

2 .... 8
-- = ---
9 ... 36

You can also do these by cross multiplying:
1) 34x = 12 * 17
x = 12 * 17 / 34
x = 12 * 1 / 2
x = 12 / 2
x = 6

2) 8x = 2 * 36
8x = 72
x = 72 / 8
x = 9

Answer 2

12/34 = 6/17


2/9 = 8/36

:)