The amplitude is the number in front of the sin word.
So, the amplitude is 3. See it? In fact, the amplitude in such questions will be the absolute value of the coefficient of the trig word given. Is this clear?
Period = 2pi divided by the coefficient of x. The coefficient of x, in this sample, is 2. See it?
P eriod = 2pi/2
Period = pi
Do you see the quantity in the parentheses?
You were given 2x - pi/2.
NOTE: It's pi NOT pie. Pie is something we eat.
To find the phase shift, set the quantity in the parentheses to 0 and solve for x.
2x - pi/2 = 0
2x = pi/2
x = pi/2 divided by 2
x = pi/4 is your phase shift.