a = amount (in oz) of solution A
b = amount of solution B
The scientist wants a mixture of 110 oz, so
a + b = 110
Solution A consists of 65% salt, so each ounce of solution A contributes 0.65 oz of salt; similarly, each ounce of B contributes 0.9 oz. The mixture is supposed to consist of 75% salt, which amounts to 0.75 * (110 oz) = 82.5 oz of salt. So
0.65 a + 0.9 b = 82.5
Solve for a and b:
b = 110 - a
0.65 a + 0.9 (110 - a) = 82.5
0.65 a + 99 - 0.9 a = 82.5
0.25 a = 16.5
a = 66 ==> b = 44
Answer:

Step-by-step explanation:
The formula of an area of a rectangle:

l - length
w - width
We have

Substitute:
<em>divide both sides by 15</em>

The formula of a perimeter of a rectangle:

Substitute:

Answer:
25
Step-by-step explanation:
420 - 45 = 375
375 / 15 = 25
Answer:
b is the correct answer. I'm 95% positive
Step-by-step explanation: