Try and subtract 3x from both sides.

distribute constants and variables on different sides of the equation.

Start with subtracting 2 from both sides and putting the ms together.

Let the number of girls be x.

therefore, number of boys = x+8

Let the first number be x.

Try to form the two equations from the information given and then work them out.

Arrange them in a linear equation and then work out the age.