Answer:
B
Explanation:
(Standard form is automatically in integers)
Multiply by 3 to take out the fraction
3y=2x+21
-2x -2x
-2x+3y=21
Standard form means Ax+By=C with positive A (usually--some people allow A to be negative).
Multiply by (-1)
2x-3y=-21
(Technically, that's the more correct answer, but since you don't have that choices, it's just the previous one.)