Let the average speed in first leg be v and let distance of first leg be x.

Then average speed in second leg is v + (v/10) = 11v/10 and distance of second leg is 2x.

Time to travel first leg: .... (1)

Time to travel second leg: .... (2)

Average speed for entire journey: .... (3)

Substitute (1) and (2) into (3) and solve for v (note that the x's cancel out).

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