If we substitute x = 21 into the equation Y = 25 - 2x, we get:
Y = 25 - 2(21)
Y = 25 - 42
Y = -17
Therefore, if x = 21, then Y = -17.
If we substitute x = 19 into the equation Y = 25 - 2x, we get:
Y = 25 - 2(19)
Y = 25 - 38
Y = -13
Therefore, if x = 19, then Y = -13.