word problem!

Question

In a recent year, companies spent a total of $89.8 billion on newspaper, television, and radio ads. The total amount spent on television and radio ads was only$3.0 billion more than the amount spent on newspaper ads alone. The amount spent on newspaper ads was $5.6 billion more than what was spent on television ads. How much was spent on each form of advertising? (Hint: Let the variables represent numbers of billions of dollars.)

Answer 1

89.8 = n+t+r

r +t = 3+ n

n = 5.6 + t

3 equations 3 unknowns, solve by substitution, elimination, or matrix algebra

graphing is difficult as it requires 3 dimensions

n+t+r = n+3+n = 2n+3 = 89.3

n = 86.3/2 = 43.15 on newspaper ads

t = n-5.6 = 37.55 on television

r = 89.3-37.55 -43.15 = 89.3 -80.7 = 8.6 on radio

t = 83.2