Answer:
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Step-by-step explanation:
since its a negative, the greater number is the lowest
36 in + 42in + 44in + 48in = 170 in
Lets call the number 'n'
plus means addition
is means the equal sign
so that as an expression would be

n+4=7
The sum of the 3 angles in a triangle is 180 , from the name you can know that it will have 3 equal angles which will be 60 degrees each as 180÷3=60
Assume you need x liters 10% acid, y liters 80% acid
Then 10%x + 80%y = 65%*70, and x+y = 70
I get: x = 15, y = 55