[5 - (5 - 2(5 - 6) + 7)] + 2= ?

[5 - (5 - 2(-1) + 7)] + 2= ?

[5 - (+3(-1) + 7)] + 2= ?

[5 - ((-1)+10)] + 2= ?      +3 + +7 = +10

[5 - (+9) + 2= ?                -1 + +10 = +9

[7- (+9)= ?                        5 + 2 =7

[7- (+9)= ?               + (+) - = -      -9 + +7 = -2

? = -2

5x+10x-4x

+10x  +  -4x  = +6x

+6x  +  +5x  = +11x

Answer is +11x

$${\mathtt{x}}{\mathtt{\,-\,}}{\mathtt{y}} = {\mathtt{x}}{\mathtt{\,-\,}}{\mathtt{y}}$$

$${\frac{{\mathtt{12\,345\,678\,910.109\: \!876\: \!543\: \!21}}}{{\mathtt{13\,579.246\: \!81}}}} = {\mathtt{909\,157.855\: \!575\: \!487\: \!293\: \!408\: \!3}}$$

$${\frac{{\mathtt{4}}}{{\mathtt{5}}}} = {\mathtt{0.8}}$$

8+8=16

I I I I I I I I + I I I I I I I I I I = I I I I I I I I I I I I I I I I

11c+21=-34

11c+21-21=-34-21

11c+21-21=-55

11c=-55

11c=-55

c=-11

Answer is -11