Hello. I hope this helps!
Let's set up an equation for this.
1st table = 83 cm
2nd table = 90 cm OR 0.9 m
3rd table = x
Total length = 250
Equation:
83 + 90 + x = 250
Now we'll solve the equation.
83 + 90 + x = 250
173 + x = 250
x = 250 - 173
x = 77 cm