Question

(x+15)2,6+x(2,6)=455
                        

Answer 1

2,6х+39+2,6х=455
5,2х=416
х=80

Answer 2

(Х+15)*2,6+х*(2,6)=455
2,6х+39+2,6х=455
5,2х+39=455
5,2=455-39
5,2х=416
Х=416:5,2
Х=80