Answer:
4 assignments of math
Explanation:
Gerald can complete a math assignment in 2 hours
Gerald can complete a physics assignment in 1 hours
Equation : 

where x is the number of completed math assignments 
 y is the number of completed science assignments. 
Since we are given that he decided to leave science assignment for the next day .
So, substitute y = 0



Hence he can complete 4 assignments of math if he decides to leave the science assignments for the next day.