Locating the mirror and detector

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see attachment

Thanks for the reply, but if it's possible, can you explain how you got the answer? Thank you.

Hi, I just drew the square and the circle then drew a line tangent to the circle passing at point (25,0) which is 5m away from the lower right hand corner. You find the mirror position at the intersection of that line and the wall.
To solve question 2 you could use the same method