c) 84:(324:18+36-x)+15=19
=> 84:(324:18+36-x)=19-15
=> 84:(324:18+36-x)=4
=> 324:18+36-x=84:4=21
=> 18+36-x = 21
=> 54-x = 21
=> x = 54-21
=> x = 33
84 : ( 18+36-x) +15= 19
84:(54-x)+15=19
84:(54-x) =19+15
84:(54-x)= 34
54-x =84:34
54-x =\(\frac{42}{17}\)
x = 54 - \(\frac{42}{17}\)
x= \(\frac{816}{17}\)