we have more than one option to solve this problem
where a is a 3 digit number and n a 1 digit number
we can replace one of the missing numbers with any number (as appropriate) and then solve to find the other value
finally we must note that it meets the characteristics
I will replace n by 2, because is a 1digit number
then
now we can solve multipliying 2 on both sides
a is 614, a is right because is a 3digit number
so, the exprssion is right
finally expression is