let
x------> the unknown number
we have
6.93*4.21 + 3.56*x + 4.21=6.93
Group terms that contain the variable x, and move the constants to the opposite side of the equation3.56*x=6.93-6.93*4.21-4.213.56*x=6.93-29.1753-4.213.56*x=-26.4553divide by 3.56x=-26.4553/3.56x=-7.43the answer is
-7.43