You have 5 blue and yellow blocks. If the blue blocks cost $2 and the yellow cost $4. How many of each can you buy if you have $16

You can buy 8 blue or 4 yellow blocks. As far as an equation

b2 + y4 = 16

there are a fixed amount of solutions but one that works is ...

2 yellow blocks and 4 blue blocks

can also do 3 yellow blocks and 2 blue blocks etc