Work out the percentage change to 2 decimal places when a price of £97 is decreased to £90

An assembly consists of two mechanical components. suppose that the probabilities that the first and second components meet specifications are 0.87 and 0.84. assume that the components are independent. determine the probability mass function of the number of components in the assembly that meet specifications. x

What is another way to express 36 +32

[10 points, algebra 2]according to my answer key the restrictions are -1 and 4. but why not positive 1?