First multiply each side of the equation by #color(red)(2)# to eliminate the fraction while keeping the equation balanced:
#color(red)(2) xx A = color(red)(2) xx 1/2h(b + b_1)#
#2A = cancel(color(red)(2)) xx 1/color(red)(cancel(color(black)(2)))h(b + b_1)#
#2A = 1h(b + b_1)#
#2A = h(b + b_1)#
Next, divide each side of the equation by #color(red)(h)# to eliminate the parenthesis while keeping the equation balanced:
#(2A)/color(red)(h) = (h(b + b_1))/color(red)(h)#
#(2A)/h = (color(red)(cancel(color(black)(h)))(b + b_1))/cancel(color(red)(h))#
#(2A)/h = b + b_1#
Now, subtract #color(red)(b_1)# from each side of the equation to solve for #b# while keeping the equation balanced:
#(2A)/h - color(red)(b_1) = b + b_1 - color(red)(b_1)#
#(2A)/h - b_1 = b + 0#
#(2A)/h - b_1 = b#
#b = (2A)/h - b_1#
