Identify the terms, like terms, coefficients and constants
2+3a+9a

Like terms in algebra are terms that have the same variables and power. Constants contain only numbers, we call them constants because their values don't change. Coefficients are the numbers in front of the variable ex: 5y in that expression 5 is the coefficient. So in the expression 2+3a+9a there is one constant which is 2 the likes terms are 3a and 9a because they have the same variable. And the coefficients are 3 and 9 because they are in front of the variable.

Like terms :  3a and 9a

Terms: All of them

Coefficients:  3 and 9

Constant : 2

I’m not sure what your trying to say here.. can you clarify again?

Determine the  wavelength of light emitted when an electron  in an li2+ ion  makes a transition from an orbital with n  =  6 to an orbital with n  = 5.