12.

1. ((a/b)+(c/d)-((1-a)/b))*(a+1)

2. (a*a+b*x+c)/2

3. (x+5)/(a+3) - (x/((b+1)*(b+1)*(b+1)))

4. (((3/4)+(2/5)) - ((1/3)-(3/2))) * (2/3)

program ct;
uses crt;
begin
    clrscr;
    writeln('1. ((a/b)+(c/d)-((1-a)/b))*(a+1)');
    delay(4000);
    writeln('2. (a*a+b*x+c)/2');
    delay(4000);
    writeln('3. (x+5)/(a+3) - (x/((b+1)*(b+1)*(b+1)))');
    delay(4000);
    writeln('4. (((3/4)+(2/5)) - ((1/3)-(3/2))) * (2/3)');
    delay(4000);
end.

Câu 1:  (a/b+c/d-(1-a)/b)*(a+1)

Câu 2:  (a*a+b*x+c)/2

Câu 3: (x+5)/(a+3)-x/((b+1)*(b+1)*(b+1))

Câu 4: ((3/4+2/5)-(1/3-3/2))*(2/3)

**Chương trình:

Program baitap;

Uses crt;

Begin

Clrscr;

Writeln('(a/b+c/d-(1-a)/b)*(a+1)');

Delay(4000);

Writeln('(a*a+b*x+c)/2');

Delay(4000);

Writeln('(x+5)/(a+3)-x/((b+1)*(b+1)*(b+1))');

Delay(4000);

Writeln('((3/4+2/5)-(1/3-3/2))*(2/3)');

Delay(4000);