(a) $9 \vec{B}-3 \vec{A} = (9(90.0), 9(-150.0)) - (3(23.0), 3(59.0)) = (810, -1350) - (69, 177) = (741, -1527)$
(b) $-5 \vec{A}+8 \vec{B} = (-5(23.0), -5(59.0)) + (8(90.0), 8(-150.0)) = (-115, -295) + (720, -1200) = (605, -1495)$
Now, we can find the magnitudes
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