19) a)400*5*4*50=2000*4*50=8000*50=40000
=(400*50)*(5*4)=2000*20=40000
b)(43+26+38)*6=107*6=642
=43*6+26*6+38*6=258+156+228=642
c)(975-860)*5=115*5=575
=975*5-860*5=4875-4300=575
21) a-scaunul mic
b-scaunul mare
a+b=1200
a/_____/
b/_____/+200
1200lei-200lei=1000lei(2a)
1000lei/2=500lei(scaunul mic)
500lei+200lei=700lei(scaunul mare)
(500lei*6)+(700lei*6)=3000lei+4200lei=7200lei(a platit familia)
SAU
1200lei*6=7200lei(a platit familia)