can you assume that any fraction is in simplest form if either the numerator or denominator is a prime number?

In most cases, if both the numerator and the denominator of a fraction are prime for example in the fraction 2/5 the greatest common factor of the numerator and denominator will be 1 which means that the fraction is in lowest terms.

However, if the numerator and the denominator are the same prime number for example 7/7 the fraction is not in lowest terms because the greatest common factor is the prime number in this case 7.

7/7 can be written in lowest terms as 1/1 therefore if the numerator and denominator of a fraction are both prime, the fraction is not always in lowest terms so the given statement is false.

some occasions yes and other no for example if a fraction was 3/9 the numerator is prime but the fraction can still be simplified to 1/3 but a number were 3/5 then you wouldn't be able to simplify it