First, add #color(red)(7)# to each side of the equation to isolate the #x# term while keeping the equation balanced:

#4sqrt(x) - 7 + color(red)(7) = 13 + color(red)(7)#

#4sqrt(x) - 0 = 20#

#4sqrt(x) = 20#

Next, divide each side of the equation by #color(red)(4)# to isolate the radical while keeping the equation balanced:

#(4sqrt(x))/color(red)(4) = 20/color(red)(4)#

#(color(red)(cancel(color(black)(4)))sqrt(x))/cancel(color(red)(4)) = 5#

#sqrt(x) = 5#

Now, square both sides of the equation to solve for #x# while keeping the equation balanced:

#(sqrt(x))^2 = 5^2#

#x = 25#