They want you determine the raw mark x such that the area under the given normal curve on the right of x be 0.18 = 18%.


It it the same as to have  the area  100%-18% = 1 - 0.18 = 0.82  under this normal curve on the left of this mark x.


So, you can use the standard function invNorm in your regular calculator TI-83 or TI-84
                 

                area  mean, SD   <<<---===  formatting pattern
    x = invNorm(0.82, 105,  12).


This way, you find x = 115.9844    ANSWER