Ken earned $8 per hour for the first 10 hours he worked, so he earned a total of $80 f or the first 10 hours he worked. For the rest of the week, Ken was paid at the rate of $10 per hour. Let x be the number of hours he will work for the rest of the week. The total of Ken’s earnings, in dollars, for the week will be 10x + 80. He saves 90% of his earnings each week, so this week he will save 0.9(10x + 80) dollars. The inequality 0.9(10x + 80) ≥ 270 represents the condition that he will save at least $270 for the week. Factoring 10 out of the expression 10x+80 gives 10(x+8). The product of 10 and 0.9 is 9, so the inequality can be rewritten as 9(x+8)≥270. Dividing both sides of this inequality by 9 yields x+8≥30, so x≥22. Therefore, the least number of hours Ken must work the rest of the week to save at least $270 for the week is 22.