Substitution word problem

I realise I posted this in the wrong forum sorry:(

this is grade 10

the problem is:

a silversmith has alloys that contain 40% silver and others that have 50% silver. A custom order requires 150g of 44% silver. How much of each alloy should be melted together to make the bracelet?

so far i got:

Let x represent the 40% alloy

Let y represent the 50% alloy.

x+y=150

0.4x+0.5y=0.44

I rearranged the first eqaution to be y=-x+150.

Then subbed it into the second to be 0.4x+0.5(-x+150)=0.44

but when I solved this, i got 745.6. Where did I go wrong?