Room Escape Prison Walkthrough:
Look at the weight set and you'll see the numbers on the weights:
Red 25, Green 15, Yellow 10
Facing the exit door, look next to the chair in the bottom left corner for a clue:
2(RED) + 3(GREEN) - YELLOW
Do the math with the weight colors and numbers:
2(25) + 3(15) - 10 = 50 + 45 - 10 = 85
Tap above the top bunk bed and enter the number 85, then take the key.
Look at the color of the bunk beds from top to bottom: Blue, Pink, Turquoise, Blue
Tap the toilet and change the colors on the side from top to bottom to blue, pink, turquoise, blue.
Take the key.