00:03
All right, we're told that this person jogs and rides his bike for a total of 75 minutes every day, and we also know that he rides 15 minutes more than he jogs.
00:11
Part a asks us to go ahead and write an equation or a system of equations for this.
00:17
They did say you let jog equal x and ride equal y.
00:21
All right, so y and x for jogging.
00:25
All right, so my first equation says that he jogs and rides for 75 minutes.
00:30
So x is the number of minutes that he jogs for.
00:33
Is the number of minutes that he rides for.
00:35
If i add those together, i get 75.
00:39
Also, we know that he rides 15 minutes more than he jogs.
00:43
So i know that the amount of minutes he rides, why, is however many minutes he jogs, plus 15, 15 more than the number of minutes he jog.
00:52
So there's my system of equations.
00:56
For part b, we're asked to actually solve, see how long does he actually jog? and our system is set up pretty nicely for a substitution.
01:05
So this one's already solved for y equals this.
01:08
So what i'm going to do is i'm going to replace y with what y is equal to.
01:12
All right.
01:12
So in my first equation, it's x plus, but instead of y, i'm going to replace it with what y is equal to, x plus 15.
01:22
And that is equal to 75.
01:25
Add your like terms, we get 2x plus 15 is equal to 75.
01:32
Subtract 15 from both sides...