$a)$

$41+27+19+13=68+19+13=87+13=100$

$55-26-16=29-16=13$

$75:3:5=25:5=5$

$b)$

$3\cdot 5+28=15+28=43$

$15\cdot 6-85=90-85=5$

$250:50+7\cdot 6=5+42=47$

$c)$

$45:5\cdot 8=9\cdot =72$

$4^2+2^3=16+8=24$

$5^3-3^2=125-9=116$

$d)$

$1500:100\cdot 3=15\cdot 3=45$

$50\cdot 30-4800:60=1500-80=1420$