Answer:

Step-by-step explanation:

nth term of an AP is given by a+(n-1)d

fourth term of an AP is a+(4-1)d= a+3d

nineteenth term of an AP is a+(19-1)d = a+18d

a+3d = -7 and a+18d =3

solving by elimination method, we get,

       a+3d=-7

   -   a+18d =3

     =-15d=-10

      =d=10/15=2/3

Answer:

CARBON DIOXIDE AND METHANE

Step-by-step explanation:

GOOD MORNING BHAIYA