+) (3x - 2) - (2x + 5) = -7
3x - 2 - 2x -5=-7;
<=>x-7=-7;
<=> x=7-7=0;
.
+) 5x - 13 = - 49 - 4x.
<=> 5x+4x=-49+13;
<=> 9x=-36;
<=> x=-4;
.
+) x + ( x +1) + ( x + 2) + …+ ( x + 30) = 496
<=> x+x+1+x+2+...+x+30=496;
<=> 31x + (1+2+..+30)=496;
<=> 31x + (1+30)+(2+29)+(3+28)+...+(14+17)+(15+16)=496
<=> 31x +31+31+...+31 =496;
<=> 31x+31.15=496;
<=> 31x + 465=496;
<=> 31x=31;
<=> x=1