Juan always saves the same amount from his weekly allowance. This table shows how much he has saved in dollars at different times. Time (wk) 3 6 9 12
Amount saved ($) $19 $28 $37 $46

Which equation represents this situation, where x is the time and y is the amount saved?

a x−3y=10
b 3x−y=10
c 3x−y=−10
d x−3y=−10