Marco and his dad went strawberry picking. Together they collected strawberries that weighed w pounds. On the way back Marco ' dad lost x pounds of strawberries. Marco's strawberries now weighed y pounds. How much did his dad's strawberries weigh now?
Let's say Marco's dad's strawberries weighed $z$ pounds. 

Then we have: 
$$w = x + z$$
$$y = z$$

So we have two equations and two unknowns. We can solve this system of linear equations using substitution. 

Substitute $z$ from the first equation into the second equation: 
$$y = w - x$$

Now we have one equation and one unknown. We can solve this equation for $y$: 
$$y = w - x$$

We know that $y = 2$, so we can plug this value into the equation and solve for $w$: 
$$2 = w - x$$
$$2 + x = w$$

We know that $x = 1$, so we can plug this value into the equation and solve for $w$: 
$$2 + 1 = w$$
$$3 = w$$

Therefore, Marco's dad's strawberries weighed 3 pounds.