Answer :
k - 45 = 18.....add 45 to both sides
k = 45 + 18
k = 63
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55 minutes - 36 minutes = 19 minutes
============================
45 minutes - 23 minutes = 22 minutes
k = 45 + 18
k = 63
============================
55 minutes - 36 minutes = 19 minutes
============================
45 minutes - 23 minutes = 22 minutes