Write an arithmetic sequences that has three arithmetic means between 155 and 215

The explicit formula for arithmetic is given by:
an = a1 + (n-1)d

In the current case,
a5 = 215
a1 = 155
n = 5

Substituting;
215 = 155 + (5-1)d
60 = 4d 
d = 60/4 = 15

Then,
a1 = 155
a2 = 155 +(2-1)15 = 170
a3 = 155 + (3-1)15 = 185
a4 = 155 + (4-1)15 = 200
a5 = 215

Therefore, the sequence is:
155,170,185,200,215