Answer:
2d +4x +9
Step-by-step explanation:
The only "like terms" are the constants, so only they can be combined.
4x + 7 + 2d + 2 = 2d + 4x + (7 + 2)
= 2d + 4x + 9
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It can be convenient to put the variables in alphabetical order, even though it isn't strictly necessary.
