When you have a scale factor as percentage, is better to convert that percentage into a fraction by divide it by 100%. That way, it will be much easier to scale your figures.
1. The scale factor we need to apply to our rectangle is 60%. Firts, lets convert our scale factor into a fraction:

. Next, we just need to multiply each side of our rectangle by our fraction:
length=

width=

So, our new rectangle will have a length of 9.6 units and a width of 4.8 units.
2. This time the scale factor is 120%. Just as before, lets convert it into a fraction:

, and just as before lets multiply each side of our triangle by our fraction:
base=

side=

So, our new isosceles triangle will have a base of 12 units and tow sides of length 9.6 units each.
3. This time the scale factor is 150%. Just as before, lets convert it into a fraction:

, and just as before lets multiply each side of our polygon by our fraction:



So, our new polygon will have a side of 12 length units, tow sides of 15 length units, and two side of 15 length units.
4. This time our factor is 75%. Just as before, lets convert it into a fraction:

, and just as before lets multiply each side of our parallelogram by our fraction:
side=

So, our new parallelogram will have tow sides of length 18.75 units.