Question 452871
A.  {{{a[1] = -7}}}, d = 1.4
==> {{{a[n] = -7 + (n-1)1.4 = -7 + 1.4n - 1.4 = 1.4n - 8.4}}}

B.  {{{a[n+1] = a[n] + 1.4}}}


C.  {{{a[50] = 1.4*50 - 8.4 = 61.6}}}

D.  {{{103.6 = 1.4n - 8.4}}} ==>  n = 80.