math % question help!!!!?

Question

a student needs 20% hydrochloric acid for a chemistry experiment how much 3% acid should be mixed with 20ML of 40% acid to get a 20% soluation

Answer 1

P is %, A is amount,
P1A1 + P2A2 = P3(A1 + A2)
3%x + 40%(20) = 20%(x + 20)
3%x + 40%(20) = 20%(x) + 20%(20)
20%(20) = 17%x
x = 400/17 = 23.53 mL.

Answer 2

let x = # of ml of 3% solution

0.03x + 0.40(20) = 0.20 ( 20 + x)

0.03x + 8 = 4 + 0.2x

0.17x = 4

x = 23.53 ml