20 POINTS Find the indicated sum. Use the formula (see attachment) for the sum of the first n terms of a geometric sequence.

Alocal concert promoter purchases 2 3/4 pages of ads. when one of the concerts is cancelled, the promoter cancels 1 5/8 pages of ads. how much advertising space is the concert promoter actually using?

Which linear equations have an infinite number of solutions? check all that apply.  (x  –  3/7)  =  2/7(3/2x  –  9/14)8(x  +  2)  =  5x  –  1412.3x  –  18  =  3(–6  +  4.1x)(6x  +  10)  =  7(x  –  2)4.2x  –  3.5  =  2.1 (5x  +  8)

Two planes leave an airport at the same time, one flying east, the other flying west. the eastbound plane travels 20 mph slower. they are 1600 mi apart after 2 hr. find the speed of each plane.