the 16th term of an AP is three times the 5th term. If the 12th term is 20 more than the 7th term find the first term and the common difference

Answer 1

Just translate the English into Math, using your definitions and properties of an AP
"the 16th term of an AP is three times the 5th term" ----> a + 15d = 3(a+4d_
a + 15d = 3a + 12d
3d = 2a
a = 3d/2

"the 12th term is 20 more than the 7th term " ---> a + 11d - (a+6d) = 20
5d = 20
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I will let you finish it ....