To combine like terms, we look for terms that have the same variable raised to the same power. In this case, we have two terms: 5m and -3m. The coefficients of these terms are 5 and -3, respectively. To combine them, we subtract the coefficient of the second term from the coefficient of the first term: 5 - 3 = 2. Therefore, we have 2m. However, since we are subtracting -3m, it is equivalent to adding 3m, resulting in 5m + 3m = 8m. The final result is 8m, which is written with the variable in descending powers, although in this case, there is only one term.