The term "a number" is going to be our variable, and we will use x to express that unknown number. The term "of" can also mean multiply, so.....
One fifth of a number = 1/5x
Three times the number = 3x
Twice the number = 2x
Now we add the other components to complete the rest of the equation:
1/5x + 3x = 2x +42
And then simplify the equation which comes down to:
x = 35
