Question 1179938
Let J = Justin's speed in km/hr
let L = Leo's speed
:
Justin can run 10 km in the same amount of time that Leo can run 12 km.
Write a time equation, time = dist/speed
j's time = L's time
{{{10/j}}} = {{{12/L}}}
cross multiply
12j = 10L
simpilfy, divide by 2
6j = 5L
:
If Leo can run 1 kph faster than Justin,
L = j + 1
or
j = L - 1 
how fast can Leo run?
Replace j with (L-1) in the first equation
6(L-1) = 5L
6L - 6 = 5L
6L - 5L = 6
L = 6 km/h is Leo's speed
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