We know that
2l + 2w = 24
And:
l = 3w
By substitution:
2(3w) +2w = 24
6w + 2w = 24
8w = 24
w = 3 metres
l = 3 x 3 = 9 metres
Total cost = 24 x $25 = $600
90
-12. The newsstand had 90 copies at the beginning of the day
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78
B > -21 is i think you answer.
BA and BD are radii of the circle, so triangle ABD is isosceles. Then angles BDA and BAD are congruent, and the remaining (central) angle ABD has measure

Angles ABD and CBD are supplementary, so

and the answer is E.
It typically just needs two parts
1) all parties must be in agreement
2) something of value needs to be exchanged. ie. money, a service