A student did 3/5 of his homework and 8 more problems. then his father came and did one fifth of the homework and the remaining 7 problems. how many problems did they solve?

Suppose the total number of problems be x

this will be given by:

(1/5) x+7 + (3/5) x+8=x

Putting like terms together we get:

(1/5x+3/5x) + (7+8) = x

4/5x+15=x

4/5x-x=-15

-1/5x=15

thus

x=75 problems

If x = total number of problems for the homework,

Student:

Number of problems done = (3/5) x + 8

Father:

Number of problems done = (1/5) x + 7

But total number of problems done is x. Then;

x = (3/5) x + 8 + (1/5) x + 7 = (4/5) x + 15

(1-4/5) x = 15

(1/5) x = 15

x = 15*5 = 75.

∴

There are 75 problems.