An automobile driver traveled the first part of a 400 mile trip at a average rate of 50 miles per hour. upon reaching an interstate route his average speed increased to 60 miles per hour his total travel time was 7 hours how far had he traveled when reached the interstate route

The distance travelled is 100 miles

Explanation:

We are given the total distance = 400 miles and total time taken = 7 hours

Given the average rate till interstate route is reached = 50 miles per hour and then rate is increased to 60 miles per hour till end of the trip.  

Let x be the distance from starting till interstate route

so time taken is given by  

and time taken for rest of the journey =  as total distance = 400

Since, total time for journey = 7 hours ,  

we get equation

=> 60x + 20000 - 50x = 21000

which gives x = 100 which is the required answer  

x = -3

y = -18

step-by-step explanation:

to solve by substitution, substitute one variable and solve for the other. then substitute again to find the remaining variable.

x-1/3(3x-9) = -3 since y=3x-9 substittute y.

x-1/3(3x-9)=-3

x + x +3 = -3

2x+3=-3

2x+3-3= -3-3

2x=-6

x=-3

substitute again into y=3x-9

y=3(-3)-9

y=-9-9

y=-18

r and t.

both are 64 degrees.