1 2/13*(3/7x-5/6)=2,5

15/13×(3/7х-5/6)=2 1/2
3/7х-5/6=5/2÷15/13
3/7х-5/6=5/2×13/15
3/7х-5/6=13/6
3/7х=13/6+5/6
3/7х=18/6
3/7х=3
х=3÷3/7
х=3×7/3
х=7