$$\left(r+1.68\right)\left(0.1\right)$$

$$0.24\cdot0.32$$

$$x=4x+15$$

$$-2\cdot\left(-1\right)-1\cdot\left(-2\right)\cdot\left(-3\right)-\left(-8\right)$$

$$\frac{d^2}{dx^2}\left(2020x^2-in\left(20-5x\right)+5e^x\right)$$

$$9x^2-3x-5+5x-9$$

$$2\ln\left(4x\right)$$