Answer:
3) 1/2 = 6/12
6) 2/3 = 4/6
9) 4/6 = 8/12
12) 3/4 = 9/12
15) 4/4 = 9/9
18) 6/9 = 4/6
Explanation:
Divide the smaller of the denominators into the larger denominator. This give you a number to multiply by the known numerator to obtain the missing numerator.
Examples:
3) 1/2 = ?/12, 12÷2 = 6, 6 ×1 = 6, so 1/2 = 6/12
4) 2/3 = ?/6, 6÷3 = 2, 2×2 = 4, so 2/3 = 4/6
etc.
etc.
etc.