Idon't understand rational and irrational numbers

A rational number is a number which can be expressed as a fraction whose numerator and denominator are both integers and whose denominator is not equal to zero. Rational numbers include all integers, fractions, mixed numbers, and some decimal numbers.

Note : All terminating and repeating decimal numbers are rational numbers because those numbers can be expressed as a fraction. On the other hand, a non repeating number and non terminating decimal, like square root of 2, is an irrational number.  

f(x)=2/3x-8, which give g(x) the greatest value.

step-by-step explanation: