There is a bag with only red marbles and blue marbles. The probability of randomly choosing a red marble is 3/10. There are 12 red marbles in the bag and each is equally likely to be chosen. Work out how many marbles in total there must be.

40

Step-by-step explanation:

Let x = total number of marbles

p(red) = (number of red marbles)/(total number of marbles)

3/10 = 12/x

3x = 120

x = 40

The total number of marbles is 40

15

step-by-step explanation:

we are given the following expression and we are to solve it and find the product:

-13 × (-5)

solving the given expression in the standard order of solving a mathematical expression, beginning with the opening of brackets and then multiplying the terms and changing their signs.

-3 × -5 = 15 (answer is positive because when negative is multiplied with negative, it gives a positive answer)