Solution: When the numerator is constant, the larger the denominator, the smaller the fractional value.

A≥B, then1/b ≥1/a;

And 4/15 =1/a+1/b, so1/b ≥ (4/15) ÷ 2 = 2/15.

That is: 1/B≥2/ 15, so the natural number b may be 1, 2,3, …, 7.

When B= 1, substitute 4/15 =1/a+1/b to get a < 0, and give up;

When B=2 and a < 0, give up;

When B=3 and a < 0, give up;

When B=4, A = 60 can be obtained.

When B=5, a =15 can be obtained;

When B=6, a =10 can be obtained;

When B=7, A= 13/ 105 can be obtained and discarded.

To sum up, the natural number A * * * has three values, namely 60, 15 and 10.

If there's a heart on it,

This number is a multiple of 52.

, so it is 26 times.

I hope it helps you.