a) $36,4\times99+36+0,4$
$=36,4\times99+36,4$
$=36,4\times(99+1)$
$=36,4\times100$
$=3640$
b) $77,28\times20,2+23,72\times20,2-20,2$
$=20,2\times(77,28+23,72-1)
$=20,2\times100$
$=2020$
c) $1,25\times59,7\times800$
$=(1,25\times8)\times100\times59,7$
$=10\times100\times59,7$
$=59700$
d) $2,5\times46+54\times2,5$
$=2,5\times(46+54)$
$=2,5\times100$
$=250$
