Question 1090127
We start by naming variables that represent how much each girl has.
Let L = number of pesos Lita has
Let R = number of pesos Rosa has
The first sentence "Lita has 15.50 pesos more than Rosa" implies that we can use addition to represent this formula.
{{{L = 15.5 + R}}}
And the second sentence "Together they have 71.50 pesos" also implies addition.
{{{L + R = 71.5}}}
So now we have two equations and two unknowns.  In order to solve we can use the substitution method.  Our first equation has an expression for L, (15.5 + R), so we can replace the L in the second equation with this expression.
{{{(15.5 + R) + R = 71.5}}}
Now we solve for R.
{{{15.5 + 2R = 71.5}}}
{{{2R = 56}}}
{{{R = 28}}}
So Rosa has 28 pesos.  To find how many Lita has, we can use either equation to solve for L.
{{{L + 28 = 71.5}}}
{{{L = 43.5}}}
Thus Lita has 43.50 pesos.