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(-3a4b3 )(-5a4b5)   Multiply like variables, multiply the coefficients,  remembering that multiplying two negative numbers give a positive result.   Multiplying variables in exponential form, we add the exponents Result (-3)(-5) =15 a4 x a4 = a8 b3 x b5 =...

Let cost of each book be x and cost of backpack =y 2x + y =26  (i) Each book cost \$8 less than a backpack  x=y-8  (ii) Substitute for x in equation (i) 2(y-8) +y = 26 2y - 16 +y =26 3y = 42 y =14 (Cost of backpack) x = cost of book =...

Because the compound is an oxide it contains only nitrogen and oxygen.  The % oxygen in the compound is 100-25.9% =74.1% Remember in empirical formula we can treat the % as having 100g of the compound, there would be 25,9 g nitrogen and 74.1 g oxygen. Steps in empirical formula 1...

The total sales figure is =107%.  Your sales before tax is =100%.  Use the ratio relationship to fine the sales before tax. 6645.16/107 = x(sales before tax)/100 Solve for x  gives you 6210.43! Check you answer  7% of 6210.43 = 434.73. Total with tax = 6645.16...

Rewrite fractions with the same denominator (preferably the lowest factor for both numbers.  This is 18 in his case. -5/6 + (-5/18) = -15/18 + (-5/18) Now that we have done that we can add the numerators  and place the answer over the denominator. -15 + (-5) = -20/18 The...