A fisherman caught 15kg fishnon Monday and 23kg on Tuesday. on Tuesday there were twice as many fish as on Monday, but their average mass was, 1|8 kg less. how many fish did the Fisherman catch on Monday?

28 fish were caught on Monday.

Let's create some equations for this problem. The following variables will be used

Fm = Fish caught on Monday

Mm = Average mass of fish caught on Monday

Ft = Fish caught on Tuesday

Mt = Average mass of fish caught on Tuesday

So we have the following equations:

15 = Fm * Mm

23 = Ft * Mt

Ft = 2 * Fm

Mt = Mm - 0.125

Let's substitute the equations for Ft and Mt into the equation for fish caught on Tuesday

23 = Ft * Mt

23 = 2 * Fm (Mm - 0.125)

23 = 2 * Fm * Mm - 2 * Fm * 0.125

23 = 2 * Fm * Mm - 0.25 * Fm

Now we know from Monday that Fm*Mm is 15, so let's substitute that into the equation and solve for Fm

23 = 2 * Fm * Mm - 0.25 * Fm

23 = 2 * 15 - 0.25 * Fm

23 = 30 - 0.25 * Fm

-7 = - 0.25 * Fm

28 = Fm

We now know that 28 fish were caught on Monday.

Let's verify that everything makes sense.

Fm = 28

Mm = 15 / 28

Ft = 2 * Fm = 2 * 28 = 56

Mt = 23 / 56

Mm - Mt = 1/8

15/28 - 23/56 = 1/8

30/56 - 23/56 = 1/8

7/56 = 1/8

1/8 = 1/8

And we get a true statement. So the calculated number of fish caught on Monday is correct.