David and Almudena have between the two 225 euros. Calculate how much money each has if Almudena has 75 euros more than David.
For this case we propose a system of equations:
x: Let the variable that represents Almudena's amount of money
y: Let the variable that represents David's amount of money
According to the statement we have:

Substituting the second equation into the first:

We find the value of the variable x:

Almudena has 150 euros
David has 75 euros
Answer:
Almudena has 150 euros
David has 75 euros
-2z^2+5z-5; Quadratic trinomial, 3 terms
-1(18+4x)=8
Then you distribute
-18-4x=8
-4x=26
X= -6.5