a)
81x27-5x[(3+3x(121:11-81:27)]:57=
2187-5x[(3+3x(11-3)]:57=
2187-5x[(3+3x8)]:57=
2187-5x[3+24]:57=
2187-5x27:57=
2187-135:57=
2187-2,368=2184,631
b)
(15:3+27:9):[16-(3x20-25x2):5-6]+3=
(5+3):[16-(60-50):5-6]+3=
8:[16-10:5-6]+3=
8:[16-2-6]+3=
8:8+3=1+3=4
c)
(X×5)+3750x4=52500
(X×5)+15000=52500
(X×5)=52500-15000
X×5=37500
X=37500:5
X=7500
d)
{[2500+(2500x2)]-6250}:5=
{[2500+5000]-6250}:5=
{7500-6250}:5=
1250:5=250