for all of the equations fiqure out which is standard and which is slope, 3x-y=7 is standard and just switch it to slope ie:
3x-y=7
+7 -7
3x-7=y
then switch around so y is in the front and vice versa, also divde any y or C by negative 1 if the answer is negative or if there is a number in front of it like in 9, and 8