Question 1128904
Hi

To solve this type of question you have to form an equation - Creating the equation is the hard bit!!

Lets say Joseph is X years old

In 20 years time this will change to X + 20

However we are also given other information 

In twenty years time Joseph will be 4 x as old as he is currently with would be 4X

So from this we can say that 

X + 20 = 4X
3X = 20
X = 20/3 ! (This seems an odd number)

6 and 2/3 

Lets check this answer

(6 and 2/3) + 20 = 26 2/3
6 2/3 x 4 = 26 2/3

These seem to work however the numbers seem very odd numbers for a question.

Is there something extra or does this sort of answer fit with the context of what you are doing?

Hope I have been of some help