Question 8430
Start by separating the equation into two groups. Let's start with {{{ab}}} and {{{7b}}}. Factor {{{b}}} from these terms to get {{{b(a + 7) - 3a - 21}}}. Next factor -3 from {{{-3a}}} and {{{-21}}} to get {{{b(a + 7) - 3(a + 7)}}}. Finally, factor {{{(a + 7)}}} to get {{{(a + 7)(b - 3)}}}