Work out the value of 4a + 2b when a = 4 and b = 3.

first substitute all the values you know into the formula (use brackets to make your work clear)

4(4) + 2(3)

we know that 2 numbers next to eachother means multiply so expand it 

4 x (4) + 2 x (3)

using BODMAS we know to do the multiplications first then add the 2 products 

16 + 6

 = 22

so 4a + 2b = 22 when a = 4 & b = 3