Answer:
White: 28 Blue: 20 Red: 32
Step-by-step explanation: Make ratios. If 35% are White strands then it would be 35/100 = ?/80 you can use the butterfly method to solve this:
35*80 = ?*100
? = 28
Blue: 25/100 = ?/80
(you can use the butterfly method or you can simplify 25/100 into 1/4)
1/4 = ?/80
1*80 = ?*4
? = 20
Red: 40/100 = ?/80 (once again, you can simplify if you want)
4/10 = ?/80
4*80 = ?*80
? = 32