Toby buy a new lamp it cost 45.50 what is the total amount his credit card charge if the sale tax 7 percent

First you set up a proportion:

7% = 7 / 100

7 x
=
100 45.50

then cross multiply:

100x = 7 ( 45.50 )

multiply:

100x = 318.5

then divide:

100x 318.5
=
100 100

x = 3.185

then add x to original price:

45.50 + 3.185 = 48.685

round to hundredths:

48.69 is your answer