Let's denote Su En's money as \( S \), Elaine's money as \( E \), and Lee Ling's money as \( L \).
From the problem, we know:
- \( S = 825 \)
- \( 0.8S = 1.5E \) (80% of Su En's money is equal to 150% of Elaine's money)
- \( L = 0.5(S + E) \) (Lee Ling has 50% of the sum of what Su En and Elaine have)
Step 1: Solve for Elaine's money
Substituting \( S = 825 \) into the equation \( 0.8S = 1.5E \):
\[ 0.8 \times 825 = 1.5E \]
Calculating the left-hand side:
\[ 660 = 1.5E \]
Now, divide both sides by \( 1.5 \) to find \( E \):
\[ E = \frac{660}{1.5} = 440 \]
Step 2: Solve for Lee Ling's money
Next, we need to find \( L \) using the equation \( L = 0.5(S + E) \):
\[ L = 0.5(825 + 440) = 0.5(1265) \]
Calculating this gives:
\[ L = 632.5 \]
Step 3: Calculate the total amount of money for all three girls
Now we can find the total amount of money by adding \( S \), \( E \), and \( L \):
\[ S + E + L = 825 + 440 + 632.5 \]
Now, performing the addition:
\[ 825 + 440 = 1265 \] \[ 1265 + 632.5 = 1897.5 \]
The total amount of money that the three girls have altogether is:
\[ \boxed{1897.5} \]