Nina is training for her upcoming speed-walking event. she walked 4/5 miles on monday, 3/4 of a mile on tuesday and 9/10 of a mile of wednesday. how many miles did she walk this week?

answer:

32oz of a

8oz of b

step-by-step explanation:

model the problem with equations

let r be her desired solution in ounces

let a represent ounces of solution a

let b represent ounces of solution b

a + b = 40 = r

0.65r = 0.6a + 0.85b     =>   0.65(40) = 0.6a + 0.85b = 26

solve the system using substitution

a + b = 40

b = 40 - a

substitute b = 40 - a into 0.6a + 0.85b = 26

0.6a + 0.85b = 26

0.6a + 0.85(40 - a) = 26

0.6a + 34 - 0.85a = 26

isolate a

8 = 0.25a

a = 32

substitute a=32 into a + b = 40

a + b = 40

32 + b = 40

isolate b

b = 8

therefore, she needs to use 32 ounces of solution a and 8 ounces of solution b to get a 40 ounce mixture that is 65% salt.