Ned's frog jumped 38\100 meter. then his frog jumped 4\10 meter. how far did ned's frog jump in all?

So first, we need to find a common denominator, make the numbers below the line equal to each other
to do this, we multiply the denominator AND numerator of 4/10 so you can get the equivilent fraction with a denominator of 100
4*10=40
10*10=100
4/10=40/100
now we add the two fractions together and we get 
38/100+40/100= 
78/100 of a meter

J= r + 9 because since jessica rode 9 more miles than roger, you add 9 miles to rogers mileage.