Question

After the addition of an acid, a solution has a volume of 90 milliliters. The volume of the solution is 3 milliliters greater than 3 times the volume of the solution before the acid was added. What was the original volume of the solution?

Answer 1

Answer: $21.75\ milliliters$

Step-by-step explanation:

Let be "x" the original volume of the solution (in milliliters) before the acid was added and "y" the volume of the solution (in milliliters) after the addition of the acid.

Set up a system of equations:

$\left \{ {{x+y=90} \atop {y=3x+3}} \right.$

Applying the Substitution Method, you can substitute the second equation into the first equation and then solve for "x":

$x+y=90\\\\x+(3x+3)=90\\\\4x+3=90\\\\x=21.75$