Question 748283
The common difference is equal to d = {{{(a[3] - a[1])/(3 - 1)}}} = {{{(18 - 4)/2 }}} = {{{7}}}. The nth term is {{{a[n] }}} = {{{a[1] + (n - 1)d}}} = {{{4 + (n-1)(7) }}} =  {{{7n - 3}}}.
The 23rd term is {{{a[23] = 7(23) - 3 = highlight(158)}}}.