I think it'd be better if you gave us some sort of diagram with it?
11/4 is the mixed fraction of that
75/100 x/56
Then do the math to find what's <span>75% of 56.</span>
We can use ratios and the cross-multiply-divide to find this.
The ratio 21:5 is avaliable via the question. We then need to compare that to the ratio x:100, the 100 being the percent and the x being the number of airplane parts.
21/5 = x/100
We can then solve for x to find the number of airplane parts. First we multiply by 100 on both sides to get 2100/5 = x. Therefore x = 420 and there are 420 airplane parts.