Y=5x+42 subtract 5x from both sides -5x+y=42 multiply by -1 5x-y=-42 In standard form, Ax+By=C, the variable A cannot be a negative. However, this is not an option so go with c.
The two events are independent, because the fact that you picked a number will not affect the result of the coin, and vice-versa, if you flip a coing and pick a number, the fact that you flipped the coin does not affect the number you will pick.