Question 551097
first number = -2
fifth number = 12
because we need to find three arithmaetic means between -2 and 12.so, totally we get 5 numbers.
this is a arithmatic series,numbers must be -2,-2+d,-2+2d,-2+3d,-2+4d
-2+4d must be equal to 12 because it is fifth number
-2+4d=12
4d=12+2=14
d=14/4=7/2=3.5

second term = -2+d=-2 + 3.5 = 1.5
third term = -2+2d = -2+2*3.5= -2+7=5
fourth term= -2+3d = -2+3*3.5 = -2+10.5=8.5

Therefore the series is -2,1.5,5,8.5,12