These problems are what is known as changing a mixed fraction to an improper fraction. Lets start with 5 1/8.
What we want to do is take the big number on the side and add it to the top of the fraction in a special way to make it an improper fraction. (An improper fraction means a fraction with a bigger top than bottom).
To add 5 to 1/8, we have to multiply 5 by 8 and then add it. 5 times 8 is 40 so if we add that to the top we know that the improper fraction we are looking for is 41/8.
We can do the same thing for 3 4/12, multiply 3 by 12 and add it to the top of the fraction. 3 times 12 is 36, add that to the top to get 40/12.
See if you can do 1 6/12 and comment with an answer, if you get it wrong I will keep helping you till we get this down!
So for example: in fraction 3 4/12 , you have to multiply 3 by 12 which will be 36 and add to the numerator in 4/12 and the answer is 40/12 in 5 1/8 , you multiply 5 by 8 which is 40 and add to numerator in 1/8 and the result is 41/8 . in 1 6/12 , you multiply 1 by 12 and add to 6/12 which is 18/12. hope you got an idea how it's solved. ( you multiply whole number by the fraction's denominator and add to the fraction's numerator)
