D. X= -4 y= 3 is the correct answer
That is a numerical expression. If it was an equation, it would have an equal sign.
The answer to this problem is simple to find the answer we must see the keywords in the sentence on of is how many which can mean addition/multiplication so here the problem is increasing in a rate of 3 3x1=3
3x2=6 3x3=9 and so on 3x7=21 your answer is 21