Let x = pounds of $12 per pound coffee
then
20-x = pounds of $9 per pound coffee
.
12x + 9(20-x) = 10(20)
12x + 180 - 9x = 200
3x + 180 = 200
3x = 20
x = 20/3
x = 6 and 2/3 pounds of $12 per pound coffee
.
Amount of $9 per pound coffee:
20-x = 20-20/3 = 60/3 - 20/3 = 40/3
or
13 and 1/3 pounds of $9 per pound coffee
C. 7.2°F is warmer than 7.0°F but colder than 7.6°F.
Remember distributive property
a(b+c)=ab+ac
we can ervers it
6(31)+6(4)-6(15)=6(31)+6(4)+6(-15)=6(31+4-15)=6(20)=120
