Measurement of <1 please help

Which addition property is being illustrated below? (type commutative or associative) (6 + 7) + 1 = 6 + (7 + 1)

The sum of two numbers is 58. the first number is 8 less than half the second number. let  c  represent the first number. let  drepresent the second number. which statements about solving for the two numbers are true? check all that apply.the equation    represents the sum of the two numbers.the equation    represents the sentence “the first number is 8 less than half the second number.”the equation    represents the relationship between the two numbers.the equation    represents the sum of the two numbers.the number  d  is 14.the number  c  is 44.the number  c  is 14.the number  d  is 44.

Find the required measurements of the following trapezoids. a = 8 cm b = 16 cm h = 10 cm