To simplify the expression 15/28 * 7/5, you can multiply the numerators together and the denominators together:

(15 * 7) / (28 * 5) = 105 / 140

Now, you can simplify the fraction by dividing both the numerator and denominator by their greatest common divisor, which is 35:

105 / 140 = (105 ÷ 35) / (140 ÷ 35) = 3/4

So, 15/28 * 7/5 simplifies to 3/4.