Let E = total earnings per month and x represents the number of items sold.
Since the expression 5x + 350 is the earnings per month, this means E = 5x + 350.
We want the earnings (E) to be "at least 950", which means we want E to be equal to 950 or larger. So we can say
E >= 950
The symbol ">=" without quotes means "greater than or equal to"
Replace the "E" with "5x+350" and solve for x
E >= 950
5x+350 >= 950
5x+350-350 >= 950-350
5x >= 600
5x/5 >= 600/5
x >= 120
So you are close, but the answer is choice C. This means she must sell 120 items or more.