Let p: the integer has one digit. let q: the integer is less than 10. which represents "the integer has one digit if and only if the integer is less than 10”? p ∨ q p ∧ q p → q p ↔ q

The double implication "if and only if" is graphically represented by an arrow pointing in both direction, so the correct writing is

it's equivalent, so we can say that its equal.

let's call the denominator x and the numerador is 18 less then denominator, x - 18.

multiply

2.x = 5.(x - 18)

2x = 5x - 90

90 = 5x - 2x

90 = 3x

x = 90/3

x = 30

so: