Let x = the number
"Ten times the sum of a number and 22 is at least 21" means
Ten times [the sum of a number and 22] is at least 21 means
10 * ( x + 22 ) ≥ 21
10(x+22) ≥ 21
10x + 220 ≥ 21 [distribute]
10x ≥ -199 [subtract 220 from both sides retains the sense of the inequality]
x ≥ -19.9 [divide both sides by 10 retains the sense of the inequality]
Check:
Use -20 [note: should be false]
Is 10(-20+22) ≥ 21 ?
10(2) ≥ 21 >
20 ≥ 21 ?no
Use 0 [note: should be true]
Is 10(0 + 22) ≥ 21 ?
220 ≥ 21 ?yes
Ten times the sum of a number 15 and is at least 21
.
2 answers
Three times the sum of a number and 21 is less than 20