How mny gals of a 20% salt solution must be mixed w/ 4 gal of a 50% salt solution to make a 30% salt solution?

Question

please hurry

Answer 1

0.2(x) + 0.5(4) = 0.3(x+4)
.2x + 2 = .3x + 1.2
2 = .1x + 1.2
0.8 = .1x
10(0.8) = .1x
8 = x

8 gallons.

Answer 2

x = amount of salt that has 20% salt solution

so if there are x gallons, the .2x is the amount of salt solution. It's added to the .5(4) = 2 gallons of the other salt solution.

When the total amount of the mixture is x + 4, in which 30% are the salt solutions

.2x + 2 = .3(x + 4)
.2x + 2 = .3x + 1.2
.1x = .8
x = 8 gallons <== answer

Answer 3

0.2X + 0.5Y = 0.3Z, Y=4
0.2X+0.5(4)=0.3Z, Z = Y+X = 4+X
0.2X+2=0.3(4+X)
0.2X+2=1.2+0.3X
0.2X-0.3X=1.2-2
-0.1X=-0.8
X=-0.8/-0.1
X= 8 GALLONS OF 20% SALT