Well try working on the problem first
One minute later at 8:01pm. One lighthouse will flash 3 times (at 20, 40 and 60 seconds)...the other will flash twice (at 30 and 60 seconds). So they will both flash 60 seconds later, at 8:01
=(-17) - 4
=(-17) + (-4)
=(-21)
70 × 20%
70 × .20 = .14
so .70 - .14 = $.56
Let the length of one of the diagonals be 2x and the other be 2y, then
cos (76/2) = x/10
x = 10 cos 38 = 7.88 cm
sin (76/2) = y/10
y = 10 sin 38 = 6.16 cm
