We can see that the rectangles are congruent meaning they can be mapped onto one another perfectly and therefore 13 and t make up a rectangle the same size and shape as the second one. This means that 13+t will add to 17 since the rectangle they make up is congruent to the second one
Use a number line if you need 4/10 - 6/10 = -2/10a simpler way is to do the opposite 6/10 - 4/10 = 2/10 then the answer would be the opposite as well. so, -2/10
