Step-by-step explanation:
It is given that,
Sam opened a savings account with a deposit of $50. Every month after that, he deposited $20 more.
It is not a proportional relationship. As initial amount was $50 and every month he deposited $20 more. The ratio is not constant for the deposited amounts.
To make the relationship proportional, he must start with zero balance and then should have deposited $20 every month.
x=9 because the triangle is equilateral which means every side is equal to 60. When you do the math you get 7x-3=60 which is 7x=63 and 63/7=9
the construction of fields of formal infinite series in several variables, generalizing the classical notion of formal Laurent series in one variable. Our discussion addresses the field operations for these series (addition, multiplication, and division), the composition, and includes an implicit function theorem.
(PDF) Formal Laurent series in several variables. Available from: https://www.researchgate.net/publication/259130653_Formal_Laurent_series_in_several_variables [accessed Oct 08 2018].