Make sure you understand the order of operations in any calculation.
Do any calculations in brackets first.
Next calculate any exponents (powers)
Then do any multiplication or division (these have equal precedence)
Finally do any addition or subtraction (these two operations have equal precedence)
4 + 5 x 6 = 4 + 30 = 34
4 + (5×2) = 4 + 10 = 14
2x2 when x = 3 is 2×32 = 2×9 = 18
Remember you can check any calculation on WolframAlpha – make sure you enter your calculation correctly.