Répondre :
a) -2x+7=3x-13
7+13=3x+2x
20=5x
x=20/5=4
b) 4-7x=-3x+1
4-1=-3x+7x
3=4x
x=3/4
c) -3(4+x)+3x=6(x+1)
-12-3x+3x=6x+6
-12=6x+6
-12-6=6x
-18=6x
x=-18/6=-3
A=(5/6)-(5/2)*(8/15)
A=(5/6)-(5/2)*(2*4/3*5)
A=(5/6)-(4/3)
A=(5/6)-(8/6)
A=-3/6=-1/2
B=(8/5)-(3/5):(9/25)
B=(8/5)-(3/5)*(25/9)
B=(8/5)-(3/5)*(5*5/3*3)
B=(8/5)-(5/3)
B=(24/15)-(25/15)=-1/15
7+13=3x+2x
20=5x
x=20/5=4
b) 4-7x=-3x+1
4-1=-3x+7x
3=4x
x=3/4
c) -3(4+x)+3x=6(x+1)
-12-3x+3x=6x+6
-12=6x+6
-12-6=6x
-18=6x
x=-18/6=-3
A=(5/6)-(5/2)*(8/15)
A=(5/6)-(5/2)*(2*4/3*5)
A=(5/6)-(4/3)
A=(5/6)-(8/6)
A=-3/6=-1/2
B=(8/5)-(3/5):(9/25)
B=(8/5)-(3/5)*(25/9)
B=(8/5)-(3/5)*(5*5/3*3)
B=(8/5)-(5/3)
B=(24/15)-(25/15)=-1/15