I will write out the equation as the wording goes, then I will only put the equation for better understanding.
A number, n, (n) is added (+)to 15 less than 3 times itself (3n -15). The result is (=) 101 (101).
Now that we have fully explained the situation, let's make our equation.
n + 3n-15 = 101.
I hope this helps, and I hope you can understand this easier as a result! :)
