It was a stale part of a quote in response to someone else.Can I prove what?
And the OP wants to understand the use of economics to understand investing. Not to give a dissertation.
Right, to understand how macro impacts investing, you need to know the concepts taught in macro and microeconomics. For example, to learn how money flows through an economy or how the spread between marginal revenue and costs impacts profits. Relationships between variables in an economy aren't static, they are dynamic. The math that helps us understand moving parts is calculus, and the study that helps us test relationships is statistics. I'd spend 2-4 hours on Khan academy to get familiar with concepts in stats and calculus (you don't need to necessarily know how to solve an equation on paper lol) before trying to do more advanced econ stuff. If you just want to know the basics of macro/micro, then the entry level textbook I suggested will suffice.