Mango tree= 5(x); guava tree= 2(x); avocado tree=8(x)... We can find x in the equation "5(x)+2(x)+8(x)=1245".. ..So, 15x=1245....x=83... We then substitute the value of x to find the no. Of trees....Mango tree=5(x)=5(83)=415..... Guava tree=2(x)=2(83)=166.... Avocado tree= 8(x)= 8(83)=664.... Therefore, there are 415 mango trees, 166 guava trees and 664 avocado trees in an orchard. :-)