To find X make an equation
9x+5=6x+26
Get the X alone on one side
9x+5-5=6x+26-5
9x=6x+21
9x-6x=6x-6x+21
3x=21
Divide
3x/3x=21/3
x=7
Insert your answer into BC
6(7)+26
42+26
BC=68