Carlos is five years older than twice his sister's age. Carlos is 13. Which equation and solution correctly identifies his sister's age?
We start by giving a label, say x, to the sister's age (you can think of x as a label on a box inside which is the number representing her age). We have to use the information we are given in order to calculate x (the number in the box).
We are told that the age of Carlos is 2*x + 5 and that this equals 13, so the equation is
2*x + 5 = 13.
Subtract 5 from both sides of this equation
2*x = 8
Divide both sides by 2
x = 4
So his sister is 4 (this is the number in the box labelled x)
We start by giving a label, say x, to the sister's age (you can think of x as a label on a box inside which is the number representing her age). We have to use the information we are given in order to calculate x (the number in the box).
We are told that the age of Carlos is 2*x + 5 and that this equals 13, so the equation is
2*x + 5 = 13.
Subtract 5 from both sides of this equation
2*x = 8
Divide both sides by 2
x = 4
So his sister is 4 (this is the number in the box labelled x)