Question 334519
Let x be the number of seats in theatre 1
Then theatre 2 is {{{x + 180}}}
And theatre 3 is {{{2x-60}}}
You are told the total seat count is 800
{{{800 = x + (x+180) + (2x-60)}}}
{{{800 = 4x + 120}}}
{{{680 = 4x}}}
{{{170 = x}}} 
theatre 1 is 170 seats
theatre 2 is {{{x+180 = 170+180 = 350}}}
theatre 3 is {{{2x-60 = 2*170 - 60 = 340-60=280}}}
Check your answer
does 170+350+280 = 800 ???