<span><span>Add: <span>14</span> + <span>27</span> = <span>1 · 74 · 7</span> + <span>2 · 47 · 4</span> = <span>728</span> + <span>828</span> = <span>7 + 828</span> = <span>1528</span> The common denominator you can calculate as the least common multiple of the both denominators - LCM(4, 7) = 28</span><span>Add: <span>1528</span> + <span>12</span> = <span>1528</span> + <span>1 · 142 · 14</span> = <span>1528</span> + <span>1428</span> = <span>15 + 1428</span> = <span>2928</span> The common denominator you can calculate as the least common multiple of the both denominators - <span>LCM(28, 2) = 28</span></span></span>