Let x be the initial width, then the initial length is x+20.
If Elise decreases this length by 8 feet, she will get the new length x+20-8=x+12.
If Elise increases the width by 10 feet, she will get the new width x+10.
The new perimeter will be x+12+x+12+x+10+x+10=4x+44=172, 4x=172-44, 4x=128, x=128÷4, x=32.
The initial width is 32 ft and the initial length is 32+20=52 ft.
The new width will be 32+10=42 ft, the new length will be 32+12=44 ft.