9514 1404 393
Answer:
Step-by-step explanation:
When x represents the number, "the sum of 3 and a number" is (x+3). Twice that sum is 2(x+3). "Is 30" means this expression is equal to 30:
2(x +3) = 30 . . . . an equation for the given conditions
__
We can solve this equation by dividing by 2:
x + 3 = 15
x = 12 . . . . . . subtract 3
The number is 12.
