Can someone explain how this equation is solved? I have it already solved but I don't understand how the outcome is got but here is the problem. Selling price=(1+r)(original cost)
63=(1+r)(42)
1.5=1+r
r=0.5

How did we go from that first part of the problem to the second; what was done exactly?

a student writes the sum of 7 times a number n plus 5 to describe thhe expression 7(n + 5). explain the error

we need sum of seven times a number plus 5

so, 7*number+5

that is, we must multiply first and then add 5 to the result. so, we get,

or, 7n+5

so, the mistake in 7(n+5) is 5 is added before multiplying. whereas ithe expression wants us to multiply 7 to the number n to get7n and then add 5 to get 7n+5 and not 7(n+5)