1. You can see that the denominator 4k+28 can be simplified to expression 4(k+7), because 4k=4·k and 28=4·7, so using the distributive property you can write that 4k+28=4(k+7).
2. Then the initial fraction becomes
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3. The nominator and the denominator have the common divisor k+7, then you can divide top and bottom by k+7: