You may have thought that $\displaystyle{\left|{6}+{\left(-{10}\right)}\right|}\usepackage{cmbright}\Huge\$ was equal to $\displaystyle-{4}\usepackage{cmbright}\Huge\$ . Remember that the absolute value of a negative number is positive, and therefore $\displaystyle{\left|{6}+{\left(-{10}\right)}\right|}={\left|-{4}\right|}={4}\usepackage{cmbright}\Huge\$ . You may have also incorrectly calculated $\displaystyle{2}\cdot{{3}}^{{2}}\usepackage{cmbright}\Huge\$ by multiplying first to get $\displaystyle{{6}}^{{2}}={36}\usepackage{cmbright}\Huge\$ . The correct order of operations is exponents before multiplication, and so $\displaystyle{2}\cdot{{3}}^{{2}}={2}\cdot{9}={18}\usepackage{cmbright}\Huge\$ .