Could someone give me a basic lesson on how to convert fractions into decimals? i have a retest coming up

Which equation represents a proportional relationship that has a constant of proportionality equal to 1/5

Tomas is making trail mix using granola and walnuts. he can spend a total of $12 on the ingredients. he buys 3 pounds of granola that costs $2.00 per pound. the walnuts cost $6 per pound. he uses the equation to represent the total cost, where x represents the number of pounds of granola and y represents the number of pounds of walnuts. he solves the equation for y, the number of pounds of walnuts he can buy. answer- b tomas added 6 to both sides of the equation instead of subtracting 6. just took the test

What is the frequency of the sinusoidal graph?