Algebra arrays
a)  Fill in the squares in the box below so that 
• the numbers across each row sum to the total at the end of the row, and • the numbers down each column also sum to the total at the bottom of the column. 
Only the numbers 1 to 7 can be used. A number can be used more than once. 

b) 
Fill in the squares in the box below so that 
• each row adds to 3x + 3y, and • each column also adds to 3x + 3y. 
