Answer:
0.9x + 3
Explanation:
0.3x + 0.6x = 0.9x
You have to combine like terms. Since 0.3x and 0.6x both have a like term of x you can combine them. However, 3 doesn't have an x like 0.3x and 0.6x therefore, you can't combine 3 with those terms
Hope this helps!