SOLUTION: when a number is divided by 10 and that quotient is decreased by 9, the result is greater than -2

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Question 1109812: when a number is divided by 10 and that quotient is decreased by 9, the result is greater than -2
Answer by Theo(13342) (Show Source):
You can put this solution on YOUR website!
let x/10 = y

let y - 9 > -2

replace y with x/10 to get:

x/10 - 9 > -2

multiply both sides of this inequality by 10 to get:

x - 90 > -20

add 90 to both sides of this inequality to get:

x > 70

that should be your solution.

take values of x to be 69, 70, 71.

your solution should be true when x = 71 and should be false when x = 69 or 70.

start with x = 69.

you get 69/10 - 9 > -2 becomes 6.9 - 9 > -2 becomes -2.1 > -2 which is false.

next go with x = 70.

you get 70/10 - 9 > -2 becomes 7 - 9 > -2 becomes -2 > -2 which is false.

finally go with x = 71.

you get 71/10 - 9 > -2 becomes 7.1 - 9 > -2 becomes -1.9 > -2 which is true.

looks like x > 70 is the solution you are looking for.

you can greaph y = x/10 - 9 and y = -2 and you will see that y = x/10 - 9 is greater than -2 when x is greater than 70.

in the graph i shows values of 60, 70, 80.

y = x/10 - 9 is not greater than -2 when x = 60 or 70, and is greater than -2 when x = 80, confirming the solution is correct.

here's the graph.