Find the missing number. 2,7,12,17, b.

Given the sequence: 2,7,12,17,
b.

We need to determine  the relation between the terms so
we can figure out the value of a and b.

We notice that the
difference between the consecutive terms 2 and 7 is
5.

Also, the difference between the consecutive terms 12
and 17 is 5 too.

Then we can conclude that we have an
arithmetical progression with the common difference between the terms is r=
5.

==> a1= 2

==>
a2 =2 + r = 2+ 5 = 7.

==> a3= 2+ 2r = 2+ 10 =
12

==> a4= 2+ 3r = 2+ 15 =
17

==> a5= 2+ 4r = 2+ 20 =
22.

==> 2, 7, 12, 17, 22 are terms of
an A.P where the first terms is 2 and common difference if
5.

==> b=
22.