The answer is 2 2/5.
To calculate 3 x 4/5, we first multiply the whole number 3 by the numerator 4 to get 12. Then, we divide the result by the denominator 5 to get 2 and a remainder of 2. Since the remainder is less than the denominator, we can express the answer as a mixed number by placing the remainder over the original denominator. So, the final answer is 2 2/5.