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.

which is the first error that tomas made?

tomas substituted the 3 for x when he should have substituted 6 for x.
tomas added 6 to both sides of the equation instead of subtracting 6.
tomas should have written the equation as .
tomas substituted 3 for x when he should have substituted 3 for y.