7 is the prime factor of 210
1st:x
2nd x+2
3rd: x+4
(x)+(x+2) = 3(x+4)-31
distribute
2x+2 = 3x+12-31
2x+2 =3x-19
subtract 2x from each side
2 = x-19
add 19 to each side
21 =x
Answer: 21,23,25
D. there is no numbers to work with so you just have to use a variable
