Y = 9/2x is in slope intercept form (y = mx+b) where m represents the slope and b represents the y-intercept.
In this case, 9/2 is the slope.

≥-4
Pretend the greater than or equal to sign is an equal sign, we will substitute it back in later.
x/2 = -4
Multiply both sides by 2 to get x alone
x = -8
Substitute the greater than or equal to sign back in and voila!
x≥-8