<span>It will take 20 minutes. The fridge needs to cool down by 90-50=40degrees. The fridge cools at 2 degrees per minute, i.e. 40/2=20 minutes total.</span>
Pairs of numbers between 1 and 6 that add up to 7: 1+6, 2+5, 3+4, 4+3, 5+2, 6+1
Pairs of numbers between 1 and 6 that add up to 8: 2+6, 3+5, 4+4, 5+3, 6+2
Pairs of numbers between 1 and 6 that add up to 9: 3+6, 4+5, 5+4, 6+3
6 for 7, 5 for 8, 4 for 9. 15 in all
X=3
6(3-2)-4(3)=8+2(3)-20
6-12=14-20
-6=-6
