to solve binomials like this there's a way called<u> </u><u>binomial</u><u> theorem</u><u> </u>given by
but for this question we need the following part
from the question we obtain that a,b and n is 3x,4 and 5since we want to find the coefficient <em>x³</em><em> </em><em> </em>k should be (5-3) = 2 so we have determined the variables now just substitute