The answer is B., based on the distributive property (multiply coeffictients, add exponents, change signs because of the negative number being multiplied)
3+3=6 therefore the answer would be 6x.
Parallel planes never touch
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.