What will come in the place of '?' in the following equation, if '+' and '–' are interchanged and also '$\times$ ' and '$÷$ ' are interchanged?$143-42\times 7÷8+21=?$

Given equation: $143-42\times 7÷8+21=?$ According to the question, we interchange the signs:$-$ becomes $+$$+$ becomes $-$$\times$ becomes $÷$$÷$ becomes $\times$ Substituting the new symbols into the equation:
$$143+42÷7\times 8-21=?$$
Now apply the BODMAS rule:Division: $42÷7=6$ $
$\text{Equation becomes: }143+6\times 8-21$$Multiplication:$ 6 \times 8 = 48
$\text{Equation becomes: } 143 + 48 - 21
Addition: $143+48=191$ $
$\text{Equation becomes: }191-21$$Subtraction:$ 191 - 21 = 170$Therefore, the value is 170.