Question 337903
18-4k<2(k+21)
18-4k<2k+42
-4k-2k<42-18
-6k<24
k>24/-6 (note the sign change when dividing by a negative value(
k>-4 ans
Proof:
Let k=-3.9
16-4*-3.9<2(-3.9+21)
16+15.6<2(17.1)
31.6<34.1