I think it’s B but I dint really know
14.1 is the correct answer i just calculated it and then subtracted
The way that i learned this was first set > to = worry about it later
so 9x-7i=3(3x-7u)
so 9x-7i=9x-21u
the x cancel out
so 7i= -21u
now isolate the variable
so
7i/-21=u
so
u=-i/3