The best and most correct answer among the choices provided by your question is the third choice or letter C "<span>commutative property of addition."
</span>The word "commutative" comes from "commute" or "move around", so theCommutative Property<span> is the one that refers to moving stuff around. For </span>addition<span>, the rule is "a + b = b + a"; in numbers, this means 2 + 3 = 3 + 2. For multiplication, the rule is "ab = ba"; in numbers, this means 2×3 = 3×2.</span>
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Answer is 180- (60+70) = 50°
Start off by knowing that the two triangle are congruent. By knowing this you can turn the given numbers into fractions.
9/72 = 7/7x+7
then cross multiply, which equals
63x + 63 = 504
then solve this equation
63x = 441 - subtract 63 from both sides
x = 7 - divide by 63 from both sides
so your answer is x=7
