First, figure out what you do and don't know....
You do know that 3 times the sum of a number and 4 is 18 more than the number....you don't know the number so you make it the variable x
now take 3 times the sum of a number and 4 and make that an expression 3x+4 this expression is the same or equal to the sum of x and 18 x+18
3x+4=x+18
2x+4=18
2x=14
x=7
hope this helped :)