Step-by-step explanation:
These problems are about like terms. Those are terms that are alike (same variables) but the coefficients (numbers in front) can be different.
1. 12m + 24m = 36m
2. 90a - 30a = 60a
Example: 6k + 8k + 10 = 14k + 10 (the part of the expression that's just a number does not combine with the parts that have variables).
3. 29b + 8
4. 36d + 25 (the terms with d in them combine--they don't have to be back-to-back)
5. This is about the Distributive Property; first multiply 14 + 15f both by 3, then look for opportunities to combine like terms.
3(14 + 15f) + 79 = 42 + 45f + 79 = 121 + 45f
6. 20(18 + 5t) - 47 + 28t = 360 + 100t - 47 + 28t
= 313 + 128t
