This problem can be solved by converting the distances into improper fractions.
To turn mixed numbers into improper fractions, simply take the whole number and multiply it by the fraction's denominator and then add the numerator. You take this new number and set it as the numerator of a fraction that has the same denominator the mixed number's fraction had (sorry if I'm confusing you). So 1 3/4 will be (1 x 4 + 3) which is 7/4. See what happened? I took the 1, multiplied it by the denominator which is 4, added 3 and got 7. This became the numerator and I kept the original denominator which was 4. The improper fraction of 1 3/4 is 7/4.
Now on to solving the problem:
We will convert the numbers one by one into improper fractions:
12 5/6 = 77/6
8 3/6 = 51/6
15 1/6 = 91/6
Since these improper fractions have the same denominator, you can add the denominators together (77+51+91) and get the fraction 219/6 or 73/2. So the total distance that the frog jumped was 73/2 inches.
-SJ