math (Reiny)
posted by peter .
If # (a,b,c,d)means you raise b,c and d to the power of a and then take the sum of the resulting values, and # (2,3,4,d)=89,then d=?
2^a + 3^a + 4^a = 89
1^a + 1^a + 1^a = 89
3^a = 89
a = 86
an I do it right

If # (a,b,c,d)means you raise b,c and d to the power of d and then take the sum of the resulting values, and # (2,3,4,d)=89,then d=?
2^d + 3^d + 4^d = 89
1^d + 1^d + 1^d = 89
3^d = 89
d = 86 
If # (a,b,c,d)means you raise b,c and d to the power of a and then take the sum of the resulting values, and # (2,3,4,d)=89,then d=?
a. 8
b. 9
c. 64
d. 81
e. 90
please answer and explain 
2 + 3^a + 4^a + d^a = 89
2 + 1^a + 1^a + d^a = 89
2^a + d^a = 87 
I don't know how to do