One fifth of a number plus three times the number is equal to twice the number plus 42 what is the number

Let the number be n.

Then n/5 + 3n = 2n + 42

Mult. all terms by 5 to eliminate the fractional coefficient 1/5:

n + 5n = 210

Then 6n = 210, and n = 210/6 = 35

Check!  Does (1/5)(35) + 3(35) = 2(35) + 42?
              Does        7      + 105   = 70 + 42?
               Does           112          = 112 ?  YES

The number is 35.