i don't under stand this: i have to replace letters w/ #'s 0-9

do+re=mi;
fa+si=la;
re+si+la=sol

In order to solve this problem, you need to replace each letter with a number from 0 to 9. The goal is to find a unique number for each letter that makes the given equations true.

Let's break it down step by step:

1. First, let's examine the equation "do + re = mi."

We need to replace the letters "d," "o," "r," "e," and "m" with numbers from 0 to 9. We can assign a unique number to each letter and try to solve the equation.

For example, let's assign the following values to the letters:
d = 2
o = 3
r = 4
e = 5
m = 7

Now substitute these values into the equation:
23 + 45 = 68

If the left-hand side of the equation (the sum of the numbers) equals the right-hand side (the result), then the chosen values are correct. If they are not equal, you need to choose different values for the letters.

2. Repeat the same process for the equation "fa + si = la."

Assign values to letters:
f = 1
a = 6
s = 8
i = 9
l = 0

Substitute the values into the equation:
16 + 89 = 05

Since this equation is not true, we need to change the values assigned to the letters and try again.

3. Lastly, let's solve the equation "re + si + la = sol."

Assign values to letters:
r = 3
e = 4
s = 0
i = 1
l = 5
o = 9

Substitute the values into the equation:
34 + 01 + 59 = 94

If the equation is true, then the values assigned to the letters are correct. If it is not true, you need to choose different values.

To summarize, you need to try different combinations of numbers for each letter and check if the equations are true. Adjust the values as needed until you find a set of numbers that makes all the equations valid.