# How would you use equations to calculate the age of Al given that Al's father is 45 and he is 15 years older than twice Al's age?

Let $x$ be Al's age, and $y$ be Al's father age. From your statement, we know that:
• $y = 45$ (Al's father is 45)
• $y = 2 x + 15$ (if you take Al's age and double it, Al's father is 15 older than that)
Combining the two expression, we observe that 45 and $2 x + 15$ are both equal to $y$, and thus must be equal. So, from $45 = 2 x + 15$ you easily get $2 x = 30$, and finally, $x = 15$