[Video] Q25: Minato drove 390 miles. part of the drive was along local roads, where his average speed was 20 miles per hour, and the rest was along a highway, where his average speed was 60 miles per hour. the drive took 8 hours. what distance, in miles, did minato drive along local roads?

Explanation for Question 25 From the Math (Calc) Section on the 2020 March Sat

So looking at number 25, we can see that we're talking about men Noto 2 who drove 390 miles, 3 and we get barely given two types of information here. 4 We're given information about the distance driven and also the amount of time driven. 5 Furthermore, we're given two types of variables that we could possibly think about, 6 right? The local roads, 7 where do we see that local roads here and also highways? 8 So since we see that we have two types of information in two variables, 9 we can think about creating a systems of equations, 10 where we have one variable dedicated to the local roads, 11 which we'll call L and one variable H which we can dedicate to the 12 highways. And now we see that Miniato drove for a total of eight 13 hours, right? So we can call L the amount of hours 14 that he drove on local roads and H the number of hours that he 15 drove on highways. 16 So if I do L plus H I should get eight, 17 right? The number of hours that he drove total. 18 And so now we need to create one more equation, 19 and we can do that using the 390 miles. 20 Now, L is an hours, and I want to get it to miles because 21 my 390 is in miles. 22 Then I can multiply by how fast Miniato drove, 23 right? If Minoso drove 20 miles per hour. 24 And I do L times 20 miles per hour, 25 we can see that if I just pretended that the units were there and 26 I multiplied the units across, I would get hours, 27 times miles divided by hours. These hours would cancel and just be left with 28 miles, which...