Question 641674
(7b-4)^2 = 144


7b-4 = sqrt(144)  or   7b-4 = -sqrt(144)


7b-4 = 12  or   7b-4 = -12


7b = 12+4  or   7b = -12+4


7b = 16   or    7b = -8


b = 16/7  or   b = -8/7


So the solutions are <font color="red">b = 16/7  or  b = -8/7</font>