Step 1) Combine the terms in parenthesis:
#(color(red)(b^8)color(blue)(c^6)color(green)(d^5))(8color(red)(b^6)color(blue)(c^2)color(green)(d)) -> color(red)(b^8)color(blue)(c^6)color(green)(d^5)8color(red)(b^6)color(blue)(c^2)color(green)(d)#
Now we can group like terms:
#color(red)(b^8)color(blue)(c^6)color(green)(d^5)8color(red)(b^6)color(blue)(c^2)color(green)(d) -> 8color(red)(b^8)color(red)(b^6)color(blue)(c^6)color(blue)(c^2)color(green)(d^5)color(green)(d)#
For the next step in the simplification we need to use the following rule for exponents:
#color(purple)(x^ax^b = x^(a+b))#
Using this rule we can now combine like terms:
#8color(red)(b^8)color(red)(b^6)color(blue)(c^6)color(blue)(c^2)color(green)(d^5)color(green)(d) -> 8color(red)(b^(8+6))color(blue)(c^(6+2))color(green)(d^(5+1)) -> 8color(red)(b^14)color(blue)(c^8)color(green)(d^6)#