Sentence is not clear, but based on what i understood :
The following sum : "4 added to a greater number" can be written as follow. Let x be that greater number (x > 4) :
"4 + x"
Then this Sum's value, is thrice the smaller number : 3 × 4 = 12.
Finally, we need to solve this equation :
4 + x = 3 × 4
4 + x = 12
We subtract 4 on both sides of the equation :
4 + x - 4 = 12 - 4
x = 8
So this number x, is equal to 8.