hi! so what you want to do is first set up a proportion, if you know that the two triangles are congruent because abc~def you know that the proportion will work out. the proportion to set up is 54/72 from there you should know that 9 goes into both 72 and 54 so when you reduce you’d be left with 6/9 which you could further reduce to 2/3. then you can find the other sides by multiplying 92 by 2/3 and you’d get 61 and 84 by 2/3 where you’d get 56. However since you are supposed to find the perimeter, you would add all three sides together (54+56+61) and you’d be left with 171. hope this helps